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2009-07-15 | Engineering of Low-Loss Metal for Nanoplasmonic and Metamaterials Applications | We have shown that alloying a noble metal (gold) with another metal
(cadmium), which can contribute two electrons per atom to a free electron gas,
can significantly improve the metals optical properties in certain wavelength
ranges and make them worse in the other parts of the spectrum. In particular,
in the gold-cadmium alloy we have demonstrated a significant expansion of the
spectral range of metallic reflectance to shorter wavelengths. The experimental
results and the predictions of the first principles theory demonstrate an
opportunity for the improvement and optimization of low-loss metals for
nanoplasmonic and metamaterials applications. | 0907.2484v1 |
2009-10-30 | Equation of state and elastic properties of face-centered-cubic FeMg alloy at ultrahigh pressures from first-principles | We have calculated the equation of state and elastic properties of
face-centered cubic Fe and Fe-rich FeMg alloy at ultrahigh pressures from first
principles using the Exact Muffin-Tin Orbitals method. The results show that
adding Mg into Fe influences strongly the equation of state, and cause a large
degree of softening of the elastic constants, even at concentrations as small
as 1-2 at. %. Moreover, the elastic anisotropy increases, and the effect is
higher at higher pressures. | 0910.5854v1 |
2010-01-21 | Jerky elasticity: Avalanches and the martensitic transition in Cu74.08Al23.13Be2.79 shape-memory alloy | Jerky elasticity was observed by dynamical mechanical analyzer measurements
in a single crystal of the shape memory alloy Cu74.08Al23.13Be2.79. Jerks
appear as spikes in the dissipation of the elastic response function and relate
to the formation of avalanches during the transformation between the austenite
and the martensite phase. The statistics of the avalanches follows the
predictions of avalanche criticality P(E) proportional to E-epsilon where P(E)
is the probability of finding an avalanche with the energy E. This result
reproduces, within experimental uncertainties, previous findings by acoustic
emission techniques. | 1001.3791v1 |
2010-03-28 | An Improved Algorithm for Generating Database Transactions from Relational Algebra Specifications | Alloy is a lightweight modeling formalism based on relational algebra. In
prior work with Fisler, Giannakopoulos, Krishnamurthi, and Yoo, we have
presented a tool, Alchemy, that compiles Alloy specifications into
implementations that execute against persistent databases. The foundation of
Alchemy is an algorithm for rewriting relational algebra formulas into code for
database transactions. In this paper we report on recent progress in improving
the robustness and efficiency of this transformation. | 1003.5350v1 |
2010-05-05 | Lifshitz tails for alloy type models in a constant magnetic field | In this note, we study Lifshitz tails for a 2D Landau Hamiltonian perturbed
by a random alloy-type potential constructed with single site potentials
decaying at least at a Gaussian speed. We prove that, if the Landau level stays
preserved as a band edge for the perturbed Hamiltonian, at the Landau levels,
the integrated density of states has a Lifshitz behavior of the type
$e^{-\log^2|E-2bq|}$. | 1005.0832v2 |
2010-06-25 | Wegner estimate for discrete alloy-type models | We study discrete alloy-type random Schr\"odinger operators on
$\ell^2(\mathbb{Z}^d)$. Wegner estimates are bounds on the average number of
eigenvalues in an energy interval of finite box restrictions of these types of
operators. If the single site potential is compactly supported and the
distribution of the coupling constant is of bounded variation a Wegner estimate
holds. The bound is polynomial in the volume of the box and thus applicable as
an ingredient for a localisation proof via multiscale analysis. | 1006.4995v1 |
2010-07-15 | Band offsets of semiconductor heterostructures: a hybrid density functional study | We demonstrate the accuracy of the hybrid functional HSE06 for computing band
offsets of semiconductor alloy heterostructures. The highlight of this study is
the computation of conduction band offsets with a reliability that has eluded
standard density functional theory. A high-quality special quasirandom
structure models an infinite random pseudobinary alloy for constructing
heterostructures along the (001) growth direction. Our excellent results for a
variety of heterostructures establish HSE06's relevance to band engineering of
high-performance electrical and optoelectronic devices. | 1007.2635v1 |
2010-09-01 | Semiconducting chains of gold and silver | The authors introduce a geometry for ultrathin Au and Ag wires that ab initio
calculations indicate to be more stable than previously considered planar
geometries for these systems, by about 0.1 eV per atom. This structure is
insulating for both metals and for related Ag_(0.5)-Au_(0.5) alloys, with gaps
of 1.3 eV for Au, 0.8 eV for Ag, and varying between 0.1 eV and 1.9 eV for the
alloys. The insulating nature of the geometry is not a result of Peierls
instabilities, and is analyzed in terms of an interplay between geometric and
electronic structure effects. | 1009.0243v1 |
2010-10-22 | On the origin of extremely high strength of ultrafine-grained Al alloys produced by severe plastic deformation | Ultrafine-grained Al alloys produced by high pressure torsion are found to
exhibit a very high strength, considerably exceeding the Hall-Petch predictions
for the ultrafine grains. The phenomena can be attributed to the unique
combination of ultrafine structure and deformation-induced segregations of
solute elements along grain boundaries, which may affect the emission and
mobility of intragranular dislocations. | 1010.4644v1 |
2010-11-03 | The pasta phase and its consequences on neutrino opacities | In this paper, we calculate the diffusion coefficients that are related to
the neutrino opacities considering the formation of nuclear pasta and
homogeneous matter at low densities. Our results show that the mean free paths
are significantly altered by the presence of nuclear pasta in stellar matter
when compared with the results obtained with homogeneous matter. These
differences in neutrino opacities certainly influence the Kelvin-Helmholtz
phase of protoneutron stars and consequently the results of supernova explosion
simulations. | 1011.0968v1 |
2011-02-25 | Capillary-Wave Model for the Solidification of Dilute Binary Alloys | Starting from a phase-field description of the isothermal solidification of a
dilute binary alloy, we establish a model where capillary waves of the
solidification front interact with the diffusive concentration field of the
solute. The model does not rely on the sharp-interface assumption, and includes
non-equilibrium effects, relevant in the rapid-growth regime. In many
applications it can be evaluated analytically, culminating in the appearance of
an instability which, interfering with the Mullins-Sekerka instability, is
similar to that, found by Cahn in grain-boundary motion. | 1102.5184v1 |
2011-04-12 | Coherent heavy quasiparticles in CePt5 surface alloy | We report on the results of a high-resolution angle-resolved photoemission
(ARPES) study on the ordered surface alloy CePt5. The temperature dependence of
the spectra show the formation of the coherent low-energy heavy-fermion band
near the Fermi level. This experimental data is supported by a multi-band model
calculation in the framework of the dynamical mean field theory (DMFT). | 1104.2165v1 |
2011-05-11 | Sigma-phase in Fe-Cr and Fe-V alloy systems and its physical properties | A review is presented on physical properties of the sigma-phase in Fe-Cr and
Fe-V alloy systems as revealed both with experimental -- mostly with the
Mossbauer spectroscopy -- and theoretical methods. In particular, the following
questions relevant to the issue have been addressed: identification of sigma
and determination of its structural properties, kinetics of alpha-to-sigma and
sigma-to-alpha phase transformations, Debye temperature and Fe-partial phonon
density of states, Curie temperature and magnetization, hyperfine fields,
isomer shifts and electric field gradients. | 1105.2179v1 |
2011-06-24 | Polytypes of long-period stacking structures synchronized with chemical order in a dilute Mg-Zn-Y alloy | A series of structural polytypes formed in an Mg-1at.%Zn-2at.%Y alloy has
been identified, which are reasonably viewed as long-period stacking
derivatives of the hcp Mg structure with alternate AB stacking of the
close-packed atomic layers. Atomic-resolution Z-contrast imaging clearly
revealed that the structures are long-period chemical-ordered as well as
stacking-ordered; unique chemical order along the stacking direction occurs as
being synchronized with a local faulted stacking of AB'C'A, where B' and C'
layers are commonly enriched by Zn/Y atoms. | 1106.4944v2 |
2011-07-31 | The weak localization for the alloy-type Anderson model on a cubic lattice | We consider alloy type random Schr\"odinger operators on a cubic lattice
whose randomness is generated by the sign-indefinite single-site potential. We
derive Anderson localization for this class of models in the Lifshitz tails
regime, i.e. when the coupling parameter $\lambda$ is small, for the energies
$E \le -C \lambda^2$. | 1108.0196v3 |
2011-09-30 | Empirical oscillating potentials for alloys from ab-initio fits and the prediction of quasicrystal-related structures in the Al-Cu-Sc system | By fitting to a database of ab-initio forces and energies, we can extract
pair potentials for alloys, with a simple six-parameter analytic form including
Friedel oscillations, which give a remarkably faithful account of many complex
intermetallic compounds. Furthermore, such potentials are combined with a
method of discovering complex zero-temperature structures with hundreds of
atoms per cell, given only the composition and the con- straint of known
lattice parameters, using molecular-dynamics quenches. We apply this approach
to structure prediction in the Al-Cu-Sc quasicrystal-related system. | 1109.6931v1 |
2011-12-11 | Single Crystal Growth of Magnesium Diboride by Using Low Melting Point Alloy Flux | Magnesium diboride crystals were grown with low melting alloy flux. The
sample with superconductivity at 38.3 K was prepared in the zinc-magnesium flux
and another sample with superconductivity at 34.11 K was prepared in the
cadmium-magnesium flux. MgB4 was found in both samples, and MgB4's
magnetization curve being above zero line had not superconductivity. Magnesium
diboride prepared by these two methods is all flaky and irregular shape and low
quality of single crystal. However, these two metals should be the optional
flux for magnesium diboride crystal growth. The study of single crystal growth
is very helpful for the future applications. | 1112.2364v1 |
2012-01-27 | Stacking-Fault Energy and Anti-Invar Effect in FeMn Alloys | Based on state-of-the-art density-functional-theory methods we calculate the
stacking-fault energy of the paramagnetic random Fe-22.5at.%Mn alloy between
300-800 K. We estimate magnetic thermal excitations by considering longitudinal
spin-fluctuations. Our results demonstrate that the interplay between the
magnetic excitations and the thermal lattice expansion is the main factor
determining the anti-Invar effect, the hcp-fcc transformation temperature, and
the stacking-fault energy, which is in excellent agreement with measurements. | 1201.5808v1 |
2012-01-30 | Thermoelectric Properties of Ho-doped Bi1-xSbx | The Seebeck coefficients, electrical resistivities, total thermal
conductivities, and magnetization are reported for temperatures between 5 and
350 K for n-type Bi0.88Sb0.12 nano-composite alloys made by Ho-doping at the 0,
1 and 3% atomic levels. The alloys were prepared using a dc hot-pressing
method, and are shown to be single phase for both Ho contents with grain sizes
on the average of 900 nm. We find the parent compound has a maximum of ZT =
0.28 at 231 K, while doping 1% Ho increases the maximum ZT to 0.31 at 221 K and
the 3% doped sample suppresses the maximum ZT = 0.24 at a temperature of 260 K. | 1201.6304v1 |
2012-03-02 | Precipitate assemblies formed on dislocation loops in aluminium-silver alloys | A detailed study of the precipitation of the \gamma' (AlAg2) phase in
undeformed aluminium-silver alloys has been conducted. Several previously
unreported features were observed, including the formation of discrete
three-dimensional assemblies comprised of 5-7 precipitates on faulted
dislocation loops. The precipitates assemblies adopted a morphology
approximating a tetrahedral bipyramidal assembly. The bounding defect of the
stacking fault was found to control both the nucleation of additional
precipitates which was responsible for the formation of the assembly structure
and also the growth characteristics of individual precipitates with these
assemblies. | 1203.0404v1 |
2012-03-22 | Tungsten silicide films for microwave kinetic inductance detectors | Microwave Kinetic Inductance Detectors (MKIDs) provide highly multiplexed
arrays of detectors that can be configured to operate from the sub-millimeter
to the X-ray regime. We have examined two tungsten silicide alloys (W5Si3 and
WSi2), which are dense alloys that provide a critical temperature tunable with
composition, large kinetic inductance fraction, and high normal-state
resistivity. We have fabricated superconducting resonators and provide
measurement data on critical temperature, surface resistance, quality factor,
noise, and quasiparticles lifetime. Tungsten silicide appears to be promising
for microwave kinetic inductance detectors. | 1203.5064v2 |
2012-03-23 | Direct observation of interacting Kondo screened 4f moments in CePt5 with XMCD | We use x-ray absorption and magnetic circular dichroism to study electronic
configuration and local susceptibility of CePt5/Pt(111) surface alloys from
well above to well below the impurity Kondo temperature. The anisotropic
paramagnetic response is governed by the hexagonal crystal field and
ferromagnetic correlations, with modified parameters for Ce moments residing
next to the alloy surface. Quantitative XMCD evaluations provide direct
evidence of Kondo screening of both spin and orbital 4f moments. Magnetic
signatures of coherence are not apparent for T >= 13 K. | 1203.5272v1 |
2012-04-26 | Magnetism: the Driving Force of Order in CoPt. A First-Principles Study | CoPt or FePt equiatomic alloys order according to the tetragonal L10
structure which favors their strong magnetic anisotropy. Conversely magnetism
can influence chemical ordering. We present here {\it ab initio} calculations
of the stability of the L10 and L12 structures of Co-Pt alloys in their
paramagnetic and ferromagnetic states. They show that magnetism strongly
reinforces the ordering tendencies in this system. A simple tight-binding
analysis allows us to account for this behavior in terms of some pertinent
parameters. | 1204.5845v1 |
2012-05-24 | Formation energy in σ-phase Fe-V alloys | Formation energy of the \sigma-phase in the Fe-V alloy system, \Delta E, was
computed in the full compositional range of its occurrence (34 < x < 60) using
the electronic band structure calculations by means of the KKR method. \Delta
E-values were found to strongly depend on the Fe concentration, also its
variation with different site occupancies was characteristic of a given lattice
site. Calculated magnetic and configuration entropy contributions were used to
determine sublattice occupancies for various compositions and temperatures. The
results agree well with those obtained from neutron diffraction measurements. | 1205.5410v1 |
2012-07-02 | Relation Between Bulk and Interface Descriptions of Alloy Solidification | From a simple bulk model for the one-dimensional steady-state solidification
of a dilute binary alloy we derive an interface description, allowing arbitrary
values of the growth velocity. Our derivation leads to exact expressions for
the fluxes and forces at the interface and for the set of Onsager coefficients.
We, moreover, discover a continuous symmetry, which appears in the low-velocity
regime, and there deletes the Onsager sign and symmetry properties. An example
is the generation of the sometimes negative friction coefficient in the
crystallization flux-force relation. | 1207.0347v1 |
2012-07-25 | Quasi-non-local gradient-level exchange-correlation approximation for metals and alloys | The flexibility of common generalized gradient approximation for the
exchange-correlation energy is investigated by monitoring the equilibrium
volume of transition metals. It is shown that no universal gradient-level
approximation yielding consistent errors for all metals exists. Based on an
element-specific optimization, the concept of quasi-non-local gradient-level
approximation is introduced. The strength of the scheme is demonstrated on
several transition metal alloys. | 1207.5923v1 |
2012-10-26 | A Phase Field Crystal Study of Solute Trapping | In this study we have incorporated two time scales into the phase field
crystal model of a binary alloy to explore different solute trapping properties
as a function of crystal-melt interface velocity. With only diffusive dynamics,
we demonstrate that the segregation coefficient, K as a function of velocity
for a binary alloy is consistent with the model of Kaplan and Aziz where K
approaches unity in the limit of infinite velocity. However, with the
introduction of wave like dynamics in both the density and concentration
fields, the trapping follows the kinetics proposed by S. Sobolev[Phys. Rev. A.
199:383386, 1995.], where complete trapping occurs at a finite velocity. | 1210.7218v1 |
2012-11-21 | Atomic scale characterization of the nucleation and growth of SnO2 particles in oxidized CuSn alloys | The internal oxidation of Sn was investigated to understand the oxidation
kinetics of monophase CuSn alloys. SnO2 particles were characterized by
analytical transmission electron microscopy. The orientation relationship
between SnO2 and Cu was determined with a special emphasis on the atomic scale
structure of Cu/SnO2 interfaces (misfit dislocations and chemical structure).
Habit planes with a pure oxygen plane terminating the SnO2 phase are greatly
favored and large misfits promote the growth of plate shaped precipitates. | 1211.5038v1 |
2012-12-21 | Critical and compensation phenomena in a mixed-spin ternary alloy: a Monte Carlo study | By means of standard and histogram Monte Carlo simulations, we investigate
the critical and compensation behaviour of a ternary mixed spin alloy of the
type $AB_pC_{1-p}$ on a cubic lattice. We focus on the case with the parameters
corresponding to the Prussian blue analog $({\rm Ni}^{\rm II}_p {\rm Mn}^{\rm
II}_{1-p})_{1.5}[{\rm Cr^{III}(CN)}_6] \cdot n {\rm H_2O}$ and confront our
findings with those obtained by some approximative approaches and the
experiments. | 1212.5483v1 |
2013-01-06 | Phase-Field Modeling of Contact Melting in Binary Alloys | Computer simulations of the phenomenon of contact melting in binary alloys
with chemical miscibility gap are performed on the basis of the phase field
theory. Kinetics of the process is examined within the isothermal
approximation, as a function of initial state. As evidenced by simulations, the
simplest phase field model is capable of reproducing the basic properties of
the phenomenon. The numerical results obtained suggest the diffusive nature of
contact melting. | 1301.1081v2 |
2013-01-25 | The Effect of mechanical alloying on Electrical properties of BaTiO3 Nano Crystals | In this paper, electrical properties of BaTiO3 nano crystals have been
studied, Barium Titanate Nano Crystals are made by mechanical alloying method
in a ball mill of SPEX 8000. In order to find Curie temperature, dielectric
constant variation via temperature and hysteresis loops are investigated. Our
results show that, there is a relationship between the time of milling and the
curie temperature .this means with increasing milling time, grain size will
decrease, consequently the curie temperature will decrease. In addition, with
increasing temperature up to the Curie temperature, the hysteresis loop of
samples decrease and at the Curie temperature the hysteresis loop changes to a
straight line. | 1301.5939v1 |
2013-03-20 | Structure, microstructure and hydrogen storage properties of melt-spun V55Ti21Cr17Fe7 and V55Ti21Mn17Fe7 | The hydrogen sorption performance of V55Ti21Cr17Fe7 and V55Ti21Mn17Fe7 alloys
and their ribbons were evaluated by pressure composition temperature tests.
Their hydrogen absorption kinetic properties were studied through hydrogen
absorption curves. The crystallographic structures and microstructure of these
alloys and ribbons before hydrogen absorption and after hydrogen desorption PCT
tests were identified by Xray diffraction and Scanning electron microscopy
analysis, respectively. Hydrogen storage characteristics of such materials were
investigated by volumetric method using Sieverts type apparatus and gravimetric
method with suspension balance. | 1303.5112v1 |
2013-04-05 | Magnetic properties of double exchange biased diluted magnetic alloy/ferromagnet/antiferromagnet trilayers | The magnetic properties of trilayers consisting of a diluted magnetic alloy,
CuMn (Cu0.99Mn0.01), a soft ferromagnet, Py(Ni0.8Fe0.2), and an
antiferromagnet, alpha-Fe2O3, were investigated. The samples, grown by UHV
magnetron sputtering, were magnetically characterized in the temperature range
T = 3-100 K. Typical exchange bias features, namely clear hysteresis cycle
shifts and coercivity enhancements, were observed. Moreover the presence of an
inverse bias, which had been already reported for spin glass-based structures,
was also obtained in a well defined range of temperatures and CuMn thicknesses. | 1304.1707v1 |
2013-07-09 | Giant magnetostriction in Tb-doped Fe83Ga17 melt-spun ribbons | Giant magnetostriction is achieved in the slightly Tb-doped Fe83Ga17
melt-spun ribbons. The tested average perpendicular magnetostriction is -886
ppm along the melt-spun ribbon direction in the Fe82.89Ga16.88Tb0.23 alloy. The
calculated parallel magnetostriction is 1772 ppm, more than 4 times as large as
that of binary Fe83Ga17 alloy. The enhanced magnetostriction should be
attributed to a small amount of Tb solution into the A2 matrix phase during
rapid solidification. The localized strong magnetocrystalline anisotropy of Tb
element is suggested to cause the giant magnetostriction. | 1307.2385v1 |
2013-08-28 | Microsegregation and dendritic growth mode of Al-5wt%Cu alloy based on non-equilibrium mush zone model | The microsegregation and dendritic growth mode of Al-5wt%Cu alloy was
investigated. In the early solidification stage, the crystal growth mode of
interrupted growth and periodic boundary trapping will happen, which results in
the segregationless dendritic grains. Microsegregation only exists at the final
solidification stage with extremely tiny residual melt fraction. In the tiny
residual melt zone, the diffusion of solute from the enriched boundary layer to
the residual melt and the convergence of enriched boundaries produce the final
microsegregation. | 1308.6034v2 |
2013-12-31 | Tuning Magnetic Properties Polycrystalline of PtCo Alloys Films with Pt | We experimentally investigated disordered PtxCo1-x (here x: 0.4, 0.5 and 0.6)
alloy thin films magnetic properties which depended on Pt content. The magnetic
properties of PtCo films were described with two effects, one of them is the
hybridization between Co 3d and Pt 5d energy levels and it causes Pt magnetic
polarization. The second one is the high spin orbit coupling constant of Pt
which increases the ratio of magnetic orbital moment to spin moment. We
investigated magnetic properties considering these effects by vibrating sample
magnetometer (VSM) and ferromagnetic resonance (FMR) techniques. | 1401.0227v2 |
2014-02-15 | Flexibility of the quasi-non-uniform exchange-correlation approximation | In our previous study [Phys. Rev. B 86, 201104 (2012)] we introduced the so
called quasi-non-uniform gradient-level exchange-correlation approximation
(QNA) and demonstrated it's strength in producing highly accurate equilibrium
volumes for metals and their alloys within the density-functional theory. In
this paper we extend the scheme to include the accuracy of bulk modulus as an
additional figure of merit and show that this scheme is flexible enough as to
allow the computation of accurate equilibrium volumes and bulk moduli at the
same time. The power and feasibility of this scheme is demonstrated on NiAl and
FeV binary alloys. | 1402.3671v1 |
2014-05-13 | Simple metal and binary alloy phases based on the hcp structure: electronic origin of distortions and superlattices | Crystal structures of simple metals and binary alloy phases based on the
close-packed hexagonal structure are analyzed within the model of Fermi
sphere-Brillouin zone interactions to understand distortions and superlattices.
Examination of the Brillouin-Jones configuration in relation to the nearly-free
electron Fermi sphere for several representative phases reveals significance of
the electron energy contribution to the phase stability. This approach may be
useful for understanding high pressure structures recently found in compressed
simple alkali and alkali-earth metals. | 1405.3044v1 |
2014-07-21 | Inclusion of intersite spatial correlations in the alloy analogy approach to the half-filled ionic Hubbard model | Using the nonlocal coherent-potential approximation we study the effect of
intersite spatial correlations on the transition from band insulator to metal
as well as from metal to Mott insulator in the "alloy analogy" approach to the
paramagnetic solution of the half-filled ionic Hubbard model. We find that
intersite spatial correlations enhance the metallic phase. | 1407.5360v1 |
2014-07-22 | Solid Solution Strengthening and Softening Due to Collective Nanocrystalline Deformation Physics | Solid solution effects on the strength of the finest nanocrystalline grain
sizes are studied with molecular dynamics simulations of different Cu-based
alloys. We find evidence of both solid solution strengthening and softening,
with trends in strength controlled by how alloying affects the elastic modulus
of the material. This behavior is consistent with a shift to collective grain
boundary deformation physics, and provides a link between the mechanical
behavior of very fine-grained nanocrystalline metals and metallic glasses. | 1407.5933v1 |
2014-07-23 | Characterisation of precipitates formed in high-pressure torsion treated Mg-3.4at.%Zn alloy | Microstructural analysis of a Mg-Zn alloy deformed at room temperature by
high-pressure torsion (HPT) indicates that fine-scale precipitation occurs even
without post-deformation heat treatment. Small-angle X-ray scattering detects
precipitates with radii between 2.5-20 nm after one rotation, with little
increase in particle size or volume fraction after 20 rotations. High
resolution electron micrographs identify grain boundary precipitates of
monoclinic Mg$_4$Zn$_7$ phase after three rotations and MgZn$_2$ after 20
rotations. | 1407.6146v2 |
2014-08-19 | Magnetoresistive property study of direct and indirect band gap thermoelectric Bi-Sb alloys | We report magnetoresistive properties of direct and indirect band gap
Bismuth-Antimony (Bi-Sb) alloys. Band gap increases with magnetic field. Large
positive magnetoresistance (MR) approaching to 400 % is observed. Low field MR
experiences quadratic growth and at high field it follows a nearly linear
behavior without sign of saturation. Carrier mobility extracted from low field
MR data, depicts remarkable high value. Correlation between MR and mobility is
revealed. We demonstrate that the strong nearly linear MR at high field can be
well understood by classical method, co-build by Parish and Littlewood. | 1408.4305v1 |
2014-11-10 | Magnetism of sigma-phase Fe-Mo alloys: its revealing and characterization | A low-temperature magnetism was revealed in a series of sigma-Fe(100-x)Mo(x)
alloys (x=45-53). Its characterization has been done using vibrating sample
magnetometry, M\"ossbauer spectroscopy, and ac magnetic susceptibility. The
magnetic ordering temperature was determined to lie in the range of 46 K for
x=45 and 22K for x=53, and the ground magnetic state was found to be typical of
a spin-glass. | 1411.2446v1 |
2014-12-12 | Magnetism of sigma-phase Fe-Mo alloys: ac magnetic susceptibility study | A series of four sigma-Fe(100-x)Mo(x) samples was investigated with ac
magnetic susceptibility measurements. An evidence was found that the ground
magnetic state of the samples is constituted by a spin glass (SG) with the spin
glass temperature ranging between ca. 34K for x=47 and ca. 16K for x=53. The SG
state is heterogeneous and it can be divided into a weak-irreversibility and a
strong-irreversibility domains. Its figures of merit are typical of metallic
(canonical) spin glasses. | 1412.4078v1 |
2015-05-22 | A combinatorial approach for studying the effect of Mg concentration on precipitation in an Al-Cu-Li alloy | We apply a combinatorial approach to study the influence of Mg concentration
on the precipitation kinetics in an Al-Cu-Li alloy using a diffusion couple
made by linear friction welding. The precipitation kinetics is monitored in the
composition gradient material using simultaneous space and time-resolved
in-situ small-angle X-ray scattering measurements during ageing, and the
strengthening of the precipitates is evaluated by micro-hardness profiles. This
data provides an evaluation of the amount of Mg necessary to promote
precipitation of the T1-Al2CuLi phase. | 1505.06126v1 |
2015-06-09 | Weak crystallization theory of metallic alloys | We extend the Weak Crystallization theory to the case of metallic alloys. The
additional ingredient -- itinerant electrons -- generates nontrivial dependence
of free energy on the angles between ordering wave vectors of ionic density.
That leads to stabilization of FCC, Rhombohedral, and icosahedral
quasicrystalline (iQC) phases, which are absent in the generic theory with only
local interactions. The condition for stability of iQC that we find, is
consistent with the Hume-Rothery rules known empirically for majority of stable
iQC; namely, the length of the primary Bragg peak wavevector is approximately
equal to the diameter of the Fermi surface. | 1506.03077v1 |
2015-08-12 | A sharp interface evolutionary model for shape memory alloys | We show the existence of an energetic solution to a quasistatic evolutionary
model of shape memory alloys. Elastic behavior of each material phase/variant
is described by polyconvex energy density. Additionally, to every phase
boundary, there is an interface-polyconvex energy assigned, introduced by M.
\v{S}ilhav\'{y}. The model considers internal variables describing the evolving
spatial arrangement of the material phases and a deformation mapping with its
first-order gradients. It allows for injectivity and orientation-preservation
of deformations. Moreover, the resulting material microstructures have finite
length scales. | 1508.02990v1 |
2015-09-15 | Application of bond valence method in the non-isovalent semiconductor alloy (GaN)$_{1-x}$(ZnO)$_x$ | This paper studies the bond valence method (BVM) and its application in the
non-isovalent semiconductor alloy (GaN)$_{\rm{1-x}}$(ZnO)$_{\rm{x}}$.
Particular attention is paid to the role of short-range order (SRO). A physical
interpretation based on atomic orbital interaction is proposed and examined by
density-functional theory (DFT) calculations. Combining BVM with Monte-Carlo
simulations and a DFT-based cluster expansion model, bond-length distributions
and bond-angle variations are predicted. The correlation between bond valence
and bond stiffness is also revealed. Finally the concept of bond valence is
extended into the modelling of an atomistic potential. | 1509.04678v2 |
2015-10-27 | Evidence for a re-entrant character of magnetism of sigma-phase Fe-Mo alloys: non-linear susceptibilities | Non-linear ac magnetic susceptibility terms viz. quadratic, chi2, and cubic,
chi3, were measured versus temperature and frequency for a series of the
sigma-phase Fe(100-x)Mo(x) (47<x<53) compounds. Clear evidence was found that
the ground magnetic state of the samples is mixed i.e. constituted by two
phases: a spin glass (SG) and a ferromagnet (FM), hence the magnetism of the
investigated samples can be regarded as re-entrant (RSG). Based on the present
data, previously reported magnetic phase diagram has been upgraded [J.
Przewoznik, S. M. Dubiel,J. Alloy. Comp., 630 (2015) 222]. | 1510.07811v1 |
2015-11-27 | Effect of interstitial-driven lattice expansion on the stacking fault energy in austenitic steels | Interstitials (carbon and nitrogen) are crucial alloying elements for
optimizing the mechanical performance of the twinning-induced plasticity (TWIP)
steels in terms of the stacking fault energy (SFE). First-principles
calculations have been performed to study the effect of interstitial-induced
lattice expansion on the SFE. Comparing the predictions with the SFEs measured
for alloys containing C and N, our results suggest that the dominant effect of
these interstitials on the SFE is due to the lattice expansion effect. | 1511.08620v1 |
2016-03-31 | Using Alloy to Formally Model and Reason About an OpenFlow Network Switch | Openflow provides a standard interface for separating a network into a data
plane and a programmatic control plane. This enables easy network
reconfiguration, but introduces the potential for programming bugs to cause
network effects. To study OpenFlow switch behavior, we used Alloy to create a
software abstraction describing the internal state of a network and its
OpenFlow switches. This work is an attempt to model the static and dynamic
behaviour a network built using OpenFlow switches. | 1604.00060v1 |
2016-10-14 | Tungsten doping of Ta3N5-Nanotubes for Band Gap Narrowing and Enhanced Photoelectrochemical Water Splitting Efficiency | Ordered W-doped Ta2O5 nanotube arrays were grown by self-organizing
electrochemical anodization of TaW alloys with different tungsten
concentrations and by a suitable high temperature ammonia treatment, fully
converted to W:Ta3N5 tubular structures. A main effect found is that W doping
can decrease the band gap from 2 eV (bare Ta3N5) down to 1.75 eV. Ta3N5
nanotubes grown on 0.5 at% W alloy and modified with (CoOH)x as co-catalyst
show ~33% higher photocurrents in photoelectrochemical (PEC) water splitting
than pure Ta3N5. | 1610.04379v1 |
2016-10-23 | Development of Yttrium alloy ion source and its application in nanofabrication | We present a new YAuSi Liquid Metal Alloy Ion Source (LMAIS), generating
focused ion beams of yttrium ions, and its prospective applications for
nanofabrication, sample preparation, lithographic and implantation processes.
Working parameters of the AuSiY LMAIS are similar to other gold-silicon based
LMAIS. We found anomalously high emission current of triple charged Yttrium
ions. Influence of Yttrium implantation on optical qualities of the implanted
ion-ensembles is shown in luminescence of co-implanted Erbium ions. | 1610.07166v1 |
2016-10-26 | Distribution of Cr atoms in a strained and strain-relaxed Fe89.15Cr10.75 alloy: Mössbauer effect study | A Fe89.15Cr10.75 alloy in a heavily strained (by cold rolling) and
strain-relaxed states was studied by means of the conversion electrons
M\"ossbauer spectroscopy (CEMS). Analysis of the spectra in terms of a
two-shell model revealed significant differences between the studied samples,
in particular, in values of the hyperfine field, a distribution of Cr atoms
within the first two neighbor-shells, the latter was expressed in terms of the
short-range order parameters, and in the magnetic texture. | 1610.08237v1 |
2018-01-04 | Quantitative aspects of the rigidity of branching microstructures in shape memory alloys via H-measures | We quantify the rigidity of branching microstructures in shape memory alloys
undergoing cubic-to-tetragonal transformations in the geometrically linearized
theory by making use of Tartar's H-measures. The main result is a
$B^{2/3}_{1,\infty}$-estimate for the characteristic functions of twins, which
heuristically suggests that the larger-scale interfaces can cluster on a set of
Hausdorff-dimension $3-\frac{2}{3}$. We provide evidence indicating that the
dimension is optimal. Furthermore, we get an essentially local lower bound for
the blow-up behavior of the limiting energy density close to a habit plane. | 1801.01338v1 |
2018-03-03 | Nickel Titanium Alloy failure analysis under thermal cycling and mechanical Loading: A Preliminary Study | The electrochemical frequency modulation (EFM) technique can consider as a
new tool for electrochemical corrosion monitoring. The calculation of corrosion
rate with a non-destructive and rapid technique is a necessity to study
corrosion behavior of metals under loading and thermal cycling. NiTi shape
memory alloy (SMA) is characterized by differential scanning calorimetry (DSC)
and uniaxial tensile testing. The corrosion behavior and reliability of
technique have been examined for NiTi sample in artificial physiological
solution. The results show the sensitivity of EFM technique to temperature and
base frequencies. | 1803.01110v1 |
2018-06-07 | Alloying-induced topological transition in 2D transition-metal dichalcogenide semiconductors | Research on two-dimensional (2D) topological insulators (TIs) is obstructed
due to the lack of feasible approaches to growing 2D TIs in experiments.
Through systematic first-principles calculations and tight-binding simulations,
we propose that alloying Os in 2D MoX2 (X = S, Se, Te) monolayers is an
effective approach to inducing semiconductor-to-TI transitions, with sizable
nontrivial gaps of 25-37 meV. Analysis of the electronic structures reveals
that the topological property mainly originates from the 5d orbitals of the Os
atom. Furthermore, the TI gaps can be modulated by external biaxial strain. | 1806.02503v2 |
2018-09-11 | Al-Cu-Fe quasicrystals as anode of lithium ion battery | In this paper, Al-Cu-Fe quasicrystal alloy was used as anode material of
lithium-ion batteries. The first specific discharge capacity of quasicrystal
was 204mAh/g. Cyclic voltammetry showed that oxidation peak of Al-Cu-Fe
quasicrystal was at about 1.4V. The reduction peak was at 0.3V. Al-Cu-Fe
quasicrystal have higher Li-ion diffusion impedance and Warburg in the first
cycle. X-ray diffraction analysis demonstrate that Li atom enter into
quasicrystal structure can not fully leave quasicrytal during first
charge/discharge cycle which induce the irreversible capacity. | 1809.03667v1 |
2018-09-28 | Thermal resistance of GaN/AlN graded interfaces | Compositionally graded interfaces in power electronic devices eliminate
dislocations, but they can also decrease thermal conduction, leading to
overheating. We quantify the thermal resistances of GaN/AlN graded interfaces
of varying thickness using ab initio Green's functions, and compare them with
the abrupt interface case. A non-trivial power dependence of the thermal
resistance versus interface thickness emerges from the interplay of alloy and
mismatch scattering mechanisms. We show that the overall behavior of such
graded interfaces is very similar to that of a thin-film of an effective alloy
in the length scales relevant to real interfaces. | 1809.11046v2 |
2017-04-04 | Continuum model for hydrogen pickup in Zirconium alloys of LWR fuel cladding | A continuum model for calculating the time-dependent hydrogen pickup
fractions in various Zirconium alloys under steam and pressured water oxidation
has been developed in this study. Using only one fitting parameter, the
effective hydrogen gas partial pressure at the oxide surface, a qualitative
agreement is obtained between the predicted and previously measured hydrogen
pickup fractions. The calculation results therefore demonstrate that H
diffusion through the dense oxide layer plays an important role in the hydrogen
pickup process. The limitations and possible improvement of the model are also
discussed. | 1704.01201v1 |
2017-04-07 | Hysteresis Behaviors of the Binary Ising Model | Hysteresis behaviors of the binary alloy system represented by the formula
$A_c B_{1-c}$ have been investigated within the framework of EFT. The system
consists of type A atoms (spin-$1$) with concentration $c$ and type B atoms
(spin-$1/2$) with concentration $1-c$. After giving the phase diagrams, we
focused on the different type of hysteresis behaviors in the system.
Especially, the mechanisms giving rise to double hysteresis behavior have been
explained, which appear at large negative values of the crystal field and low
temperatures. It has been observed that binary alloy system could exhibit DH
behavior in region $0<c<0.557$. Besides, dependence of hysteresis loop area,
coercive field and remanent magnetization on the concentration has been
investigated. | 1704.02140v1 |
2017-04-21 | The Effects of Rolling Deformation and Annealing Treatment on Damping Capacity of 1200 Aluminium Alloy | Annealing treatment is an important step of rolling deformation that
contributes to microstructural evolution and leads to the significant changes
in damping capacity. Damping capacities were analyzed in the parallel to
rolling direction at 1 and 10 Hz respectively. It was found that severe plastic
deformation at 40 percent reduction has lower damping capacity compared to that
of 30 percent and 20 percent reductions respectively. The microstructural
results show that the grains of as rolled alloys were changed to almost
equiaxed structures after a rolling reduction at 40 percent reduction. | 1704.07362v1 |
2017-05-31 | Collisions in shape memory alloys | We present here a model for instantaneous collisions in a solid made of shape
memory alloys (SMA) by means of a predictive theory which is based on the
introduction not only of macroscopic velocities and temperature, but also of
microscopic velocities responsible of the austenite-martensites phase changes.
Assuming time discontinuities for velocities, volume fractions and temperature,
and applying the principles of thermodynamics for non-smooth evolutions
together with constitutive laws typical of SMA, we end up with a system of
nonlinearly coupled elliptic equations for which we prove an existence and
uniqueness result in the 2 and 3 D cases. Finally, we also present numerical
results for a SMA 2D solid subject to an external percussion by an hammer
stroke. | 1705.11121v1 |
2018-10-18 | Strengthening of copper by carbon nanotubes | The influence of a modifier based on multi walled carbon nanotubes (MWCNT) is
investigated using C11000 copper alloy. The influence of the modifier addition
into the melt was investigated using tensile test, hardness measurements, X-ray
diffraction method and microstructural investigations. It was evaluated that
the yield and tensile strengths of the metal increased due to the
microstructural changes in the formed metal after addition of 0.01wt.% of the
MWCNTs. It was also evaluated that the addition of mentioned amount of MWCNT
into alloy has no influence to the phase composition of the formed metal. | 1810.08019v1 |
2019-01-06 | Enhanced magnetic ordering in Sm metal under extreme pressure | The dependence of the magnetic ordering temperature To of Sm metal was
determined through four-point electrical resistivity measurements to pressures
as high as 150 GPa. A strong increase in To with pressure is observed above 85
GPa. In this pressure range Sm ions alloyed in dilute concentration with
superconducting Y exhibit giant Kondo pair breaking. Taken together, these
results suggest that for pressures above 85 GPa Sm is in a highly correlated
electron state, like a Kondo lattice, with an unusually high value of To. A
detailed comparison is made with similar results obtained earlier on Nd, Tb and
Dy and their dilute magnetic alloys with superconducting Y. | 1901.01563v1 |
2019-07-24 | Chemical complexity in high entropy alloys: A pair-interaction perspective | The recently proposed pair-interaction model is applied to study a series of
refractory high entropy alloys. The results demonstrate the simplicity,
robustness, and high accuracy of this model in predicting the configuration
energies of NbMoTaW, NbMoTaWV and NbMoTaWTi. The element-element pair
interaction parameters obtained from the linear regression of first-principle
data provide a new perspective to understand the strengthening mechanism in
HEAs, as revealed by comparing the effects of adding vanadium and titanium.
Using the pair-interaction model, an expression for the intrinsic energy
fluctuation is derived, which provides guidance on both theoretical modeling
and first principles calculation. | 1907.10223v1 |
2012-09-21 | Multicolour wavelength-tunable lasing from a single bandgap-graded alloy nanoribbon | Tunable lasing from 578 nm to 640 nm is observed from a single CdSSe
bandgap-graded alloy nanoribbon, by selecting the excited spot at room
temperature. Though reabsorption is a serious problem to achieve lasing at
short wavelength, multiple scatters on the nanoribbon form localized cavities,
and thus realize lasing at different wavelengths. By increasing the excitation
area, we also observe multicolour lasing from the same nanoribbon
simultaneously. | 1209.4704v1 |
2012-09-27 | Unique Truncated Cluster Expansions for Materials Design via Subspace Projection and Fractional Factorial Design | For alloy thermodynamics, we obtain unique, physical effective cluster
interactions (ECI) from truncated cluster expansions (CE) via
subspace-projection from a complete configurational Hilbert space; structures
form a (sub)space spanned by a locally complete set of cluster functions.
Subspace-projection is extended using Fractional Factorial Design with subspace
"augmentation" to remove systematically the ECI linear dependencies due to
excluded cluster functions - controlling convergence and bias error, with a
dramatic reduction in the number of structural energies needed. No statistical
fitting is required. We illustrate the formalism for a simple Hamiltonian and
Ag-Au alloys using density-functional theory. | 1209.6176v1 |
2014-06-30 | Influence of model asymmetry on kinetic pathways in binary Fe-Cu alloy: a kinetic Monte Carlo study | A kinetic Monte Carlo simulations with model asymmetry in binary Fe-Cu alloy
leading to the same microstructure are presented. A method based on
thermodynamic data for calculation of interatomic potentials dependent on model
asymmetry is presented and evaluated. Results show that kinetic pathways are
sensitive to model asymmetry and are compared to the classical growth and
coarsening theories. Experimental diffusion data is used and compared to
simulation results to determine a realistic combination for simulations. | 1406.7839v2 |
2018-01-13 | Electrochemical and mechanical behaviors of dissimilar friction stir welding between 5086 and 6061 aluminum alloy | The electrochemical behavior and mechanical properties of friction stir
welded AA5086 and AA6061 Al alloys were investigated. Micro-hardness
measurements and tensile tests showed that the heat-affected zone (HAZ) in
AA6061 had minimum hardness value (i.e., 88 HV) and served as failure site in
the dissimilar weld. Corrosion testing revealed that the minimum value of Icorr
appeared in the HAZ 5086 (0.54 uA/cm2) and HAZ 5086 was most resistant to
corrosion. The AA 5086 side of the weld showed better corrosion resistance than
the AA 6061 side. | 1802.03460v1 |
2018-02-16 | The mechanisms of hot salt stress corrosion cracking in titanium alloy Ti-6Al-2Sn-4Zr-6Mo | Hot salt stress corrosion cracking in Ti 6246 alloy has been investigated to
elucidate the chemical mechanisms that occur. Cracking was found to initiate
beneath salt particles in the presence of oxidation. The observed transgranular
fracture was suspected to be due to hydrogen charging; XRD and high-resolution
transmission electron microscopy detected the presence of hydrides that were
precipitated on cooling. SEM-EDS showed oxygen enrichment near salt particles,
alongside chlorine and sodium. Aluminium and zirconium were also involved in
the oxidation reactions. The role of intermediate corrosion products such as
Na2TiO3, Al2O3, ZrO2, TiCl2 and TiH are discussed. | 1802.06045v1 |
2018-08-15 | On the characterisation of a hitherto unreported icosahedral quasicrystal phase in additively manufactured aluminium alloy AA7075 | Aluminium alloy AA7075 (Al-Zn-Mg-Cu) specimens were prepared using selective
laser melting, also known as powder bed fusion additive manufacturing. In the
as-manufactured state, which represents a locally rapidly solidified condition,
the prevalence of a previously unreported icosahedral quasicrystal with 5-fold
symmetry was observed. The icosahedral quasicrystal, which has been termed
nu-phase, was comprised of Zn, Cu and Mg. | 1808.05033v1 |
2018-08-31 | On the miscibility gap at 800 K in the Fe-Cr alloy system | Issues pertinent to the miscibility gap at 800K in a Fe73.7Cr26.3 alloy viz.
the kinetics of the phase decomposition and borders of the latter were
investigated by means of the M\"ossbauer-effect spectroscopy. The kinetics was
revealed to well follow the Johnson-Mehl-Avrami-Kolgomarov equation testifying
to a nucleation and growth mechanism underlying the decomposition. A solubility
limit of Cr in the Fe matrix was determined to be 17.3(6) at.% and that of Fe
in the Cr matrix was found as equal to 18.5(9) at.%. The results obtained have
been compared with various theoretical predictions. | 1808.10763v1 |
2020-04-27 | Temperature dependence of the anomalous Nernst effect in Ni$_{2}$MnGa shape memory alloy | We report a detailed investigation of the Ni$_{2}$MnGa shape memory alloy
through magnetic, electronic, and thermal measurements. Our measurements of the
anomalous Nernst effect (ANE) reveal that this technique is very sensitive to
the onset of the pre-martensitic transition in sharp contrast to other
transport measurements. With the ANE being sensitive to changes at the Fermi
surface, we infer on the link between the structural modulations and the
modulation of the Fermi surface via its nesting features, with the magnetic
field induced strain being the mediating mechanism. | 2004.12562v1 |
2021-03-12 | Incorporation of Si atoms into CrCoNiFe high-entropy alloy: a DFT study | Density functional theory based computational study has been conducted in
order to investigate the effect of substitution of Cr and Co components by Si
on the structure, mechanical, electronic, and magnetic properties of the high
entropy alloy CrCoNiFe. It is found that the presence of a moderate
concentration of Si substitutes (up to 12.5 %) does not significantly reduce
the structural and mechanical stability of CrCoNiFe while it may modify its
electronic and magnetic properties. Based on that, Si is proposed as a cheap
and functional material for partial substitution of Cr or Co in CrCoNiFe. | 2103.07322v1 |
2022-02-12 | Spin-orbit driven terahertz optical response in ferromagnetic Fe-Co-Al alloys | We study the magneto-optical properties of Fe-Co-Al ordered alloys in the
terahertz range of frequencies. We find that magnetism can modify the
reflection of light from these magnets and that this modification strongly
depends on the frequency of incoming light in the terahertz range. For example,
we find that below 10~THz Co$_3$Al has nearly constant $\sigma_{xy}$ and that
above 10~THz it is reduced by about 50 times. Furthermore, we find a strong
dependence of $\sigma_{xy}$ on chemical composition. For example, we find that
the addition of Al to Fe changes the sign of $\sigma_{xy}$, while the addition
of Co to Fe leads to non-monotonic dependence of $\sigma_{xy}$ on
Co-concentration. | 2202.05997v1 |
2016-12-08 | First-principles study on the magnetic properties of ordered Nd$_{6}$(Fe,Ga)$_{14}$ alloys | We studied the stable magnetic structure of ordered Nd$_{6}$Fe$_{14-x}$Ga$_x$
($x = 0, 1)$ alloys, which appears in the grain-boundary (GB) phase of Nd-Fe-B
permanent magnets, using first-principles techniques. Slight Ga doping ($x =
1$) was shown to contribute to the stabilization of an anti-ferromagnetic (AF)
state, whereas the non-doped case ($x = 0$) was revealed to favor ferromagnetic
state rather than AF state with a slight energy difference. | 1612.02633v3 |
2016-12-11 | Accurate representation of formation energies of crystalline alloys with many components | In this paper I propose a new model for representing the formation energies
of multicomponent crystalline alloys as a function of atom types. In the cases
when displacements of atoms from their equilibrium positions are not large, the
proposed method has a similar accuracy as the state-of-the-art cluster
expansion method, and a better accuracy when the fitting dataset size is small.
The proposed model has only two tunable parameters - one for the interaction
range and one for the interaction complexity. | 1612.03359v2 |
2018-04-07 | A new ab initio modeling scheme for ion self-diffusion coefficient applied for ε-Cu3Sn phase of Cu-Sn alloy | We present a new modeling scheme for ion self-diffusion coefficient, which
broadens the applicable scope of ab initio approach. The essential concepts of
the scheme are `domain division' and `coarse graining' of the diffusion network
based on the barrier energies predicted by the ab initio calculation. The
scheme was applied to evaluate Cu ion self-diffusion coefficient in
{\epsilon}-Cu3Sn phase of Cu-Sn alloy, which is a typical system having
long-range periodicity. The model constructed with the scheme successfully
reproduces the experimental values in a wide temperature range. | 1804.02535v2 |
2018-04-09 | Superconductivity in REO0.5F0.5BiS2 with high-entropy-alloy-type blocking layers | We synthesized new REO0.5F0.5BiS2 (RE: rare earth) superconductors with the
high-entropy-alloy-type (HEA-type) REO blocking layers. According to the RE
concentration and the RE ionic radius, the lattice constant of a systematically
changed in the HEA-type samples. A sharp superconducting transition was
observed in the resistivity measurements for all the HEA-type samples, and the
transition temperature of the HEA-type samples was higher than that of typical
REO0.5F0.5BiS2. The sharp superconducting transition and the enhanced
superconducting properties of the HEA-type samples may indicate the
effectiveness of the HEA states of the REO blocking layers in the
REO0.5F0.5BiS2 system. | 1804.02880v2 |
2019-03-18 | Morphology, ordering, stability, and electronic structure of carbon-doped hexagonal boron nitride | We present theoretical studies of morphology, stability, and electronic
structure of monolayer hexagonal CBN alloys with rich content of h-BN and
carbon concentration not exceeding 50 %. Our studies are based on the bond
order type of the valence force field to account for the interactions between
atomic constituents and Monte Carlo method with Metropolis algorithm to
establish equilibrium distribution of atoms over the lattice. We find out that
the phase separation into graphene and h-BN domains occurs in the majority of
growth conditions. Only in N-rich growth conditions, it is possible to obtain
quasi uniform distribution of carbon atoms over boron sublattice. We predict
also that the energy gap in stoichiometric C$_x$(BN)$_{1-x}$ alloys exhibits
extremely strong bowing. | 1903.07357v1 |
2019-03-19 | Exchange Interaction in Fe$_{1-x}$Ni$_{x}$Alloys: XPS Study | In this paper, high Fe-concentration Fe$_{1-x}$Ni$_{x}$ alloys were
investigated using high resolution X-ray photoelectron spectroscopy (XPS) down
to 10K temperature. The Fe 2s core level exhibits three features, two low
binding features corresponding to exchange interaction between ionized 2s core
level and the unpaired 3d electrons. The high binding energy feature
corresponds to the screening of 2s core hole by 4s conduction electrons. Our
studies suggest high local magnetic moments on Fe sites. | 1903.08227v3 |
2019-05-03 | Prospects to attain room temperature superconductivity | With a generic model for the electron-phonon spectral density, two simple
expressions are derived to estimate the transition temperature and
gap-to-temperature ratio in conventional superconductors. They entail that on
average the numerical value of the phonon exchange factor, $\lambda$, is
limited to 2.67, so that room temperature superconductivity may be attained
only with a Debye temperature of about 1800 K or higher, in materials that may
or may not involve hydrogen. They also show that a Be-Pb alloy may become a
superconductor at $\sim$44 K. | 1905.01367v2 |
2019-12-03 | Thermomechanical model for NiTi-based shape memory alloys covering macroscopic localization of martensitic transformation | The work presents a thermomechanical model for polycrystalline NiTi-based
shape memory alloys developed within the framework of generalized standard
solids, which is able to cover loading-mode dependent localization of the
martensitic transformation. The key point is the introduction of a novel
austenite-martensite interaction term responsible for strain-softening of the
material. Mathematical properties of the model are analyzed and a suitable
regularization and a time-discrete approximation for numerical implementation
to the finite-element method are proposed. Model performance is illustrated on
two numerical simulations: tension of a superelastic NiTi ribbon and bending of
a superelastic NiTi tube. | 1912.01356v1 |
2019-12-16 | Synthesis of Electron- and Hole-Doped Bulk BaFe2As2 Superconductors by Mechanical Alloying | Here, we report the successful synthesis of electron- (Ni) and hole- (K)
doped bulk BaFe2As2 compounds by means of mechanical alloying (MA) process. The
MA technique allows one to obtain amorphous phase BaFe2As2 with a homogeneous
distribution of doping atoms at room temperature without continuous heating. We
found the optimum time for high-energy milling is in the range between 1-1.5
hours. Using pre-synthesised FeAs and NiAs precursors, we successfully obtained
BaFe2-xNixAs2 and Ba1-xKxFe2As2 superconducting bulk samples after short-range
heat treatment. This method can be easily scaled according to industrial needs
to provide high-quality bulk superconducting material for wires, trapped field
magnets and other applications. | 1912.07264v1 |
2020-06-03 | Localized pore evolution assisted densification during spark plasma sintering of nanocrystalline W-5wt.%Mo alloy | The present work reports the role of different atomic mobility induced
localized pore evolution on densification during spark plasma sintering of
nanocrystalline W-Mo alloy powder. The shrinkage (or expansion) behavior of
cold compacted milled powders was studied using dilatometry during
non-isothermal sintering up to 1600 {\deg}C. Subsequently, the milled powders
were densified to ~95% relative density using spark plasma sintering up to 1600
{\deg}C. The enhanced localized Joule heating due to dynamically evolved porous
structure could be attributed for the densification during spark plasma
sintering. | 2006.02340v1 |
2020-07-22 | Magnetocaloric properties of the binary Ising model with arbitrary spin | The magnetocaloric properties of the Ising binary alloys composed of
arbitrary spin values, have been determined by using effective field theory.
For determining the efficiency of the magnetocaloric effect in binary alloy,
the quantities of interest such as isothermal magnetic entropy change and
refrigerant capacity have been calculated for various values of spin and
concentration. It is shown that, by changing the concentration we can tune the
magnetocaloric performance. Also, it has been shown that greater refrigerant
capacity can be obtained for intermediate concentration values, in comparison
with the limiting concentration values. | 2007.11310v1 |
2020-09-01 | Solute softening and vacancy generation by diffusion-less climb in magnesium alloys | Active room temperature diffusion-less climb of the <a> edge dislocations in
model Mg-Al alloys was observed using molecular dynamics simulations.
Dislocations on prismatic and pyramidal I planes climb through the basal plane
to overcome solute obstacles. This out-of-plane dislocation motion softens the
high resistance pyramidal I glide and significantly reduces the anisotropy of
dislocation mobility, and could help improve the ductility of Mg. The flow
stress scales linearly with solute concentration, cAl. Dislocations climb
predominantly in the negative direction, with climb angle on the order of
0.01cAl, producing very high vacancy concentration on the order of 10-4. | 2009.00656v1 |
2020-11-24 | Hysteresis Characteristics of Generalized Spin-S Magnetic Binary Alloys | In this study, hysteresis characteristics of the generalized spin-S binary
alloy represented by the formula $A_c B_{1-c}$ have been investigated within
the framework of effective field approximation. The binary system consists of
type A (spin-S) and type B (spin-S) atoms which are randomly distributed on a
honeycomb lattice. Both integer and half-integer spin models of two magnetic
atom types are examined. By detailed investigation on hysteresis loops,
multiple hysteresis behaviors are obtained for a given set of Hamiltonian
parameters. Besides, the quantities of hysteresis characteristics as the
hysteresis loop area, remanent magnetization, and coercive field have been
investigated as functions of concentration. | 2011.12337v1 |
2020-11-23 | Non rectification of heat in graded Si-Ge alloys | We investigate the possibility to obtain a thermal diode with functionally
graded Si-Ge alloys. A wire with variable section is considered. After the
introduction of a formula giving the thermal conductivity of the wire as a
function of the species content and of the diameter of the wire, numerical and
analytical results are presented supporting the impracticability to get a
thermal diode with the characteristics here considered. However, the present
study opens the way to further generalisations amenable to give applicative
promising results. | 2012.03668v1 |
2021-04-14 | The Portevin-Le Chatelier Effect and Beyond | The chapter presents the problem of the complexity of plastic flow in alloys,
which is manifested by serrated deformation curves and transient plastic strain
localizations. This phenomenon uncovers an inherently collective nature of the
dynamics of crystal defects. The chapter discusses the state-of-the art of this
research under the angle of distinct regimes of collective dislocation dynamics
found in conventional, basically binary alloys, e.g., self-organized
criticality, deterministic chaos, or synchronization. It concludes with the
formulation of diverse open questions, notably concerning manifestations of the
collective dislocation dynamics pertaining to finer scales of plastic
deformation processes, as compared to the macroscopic plastic instability. | 2104.07018v1 |
2021-05-27 | Experimental validation of density functional theory calculations on the Zr/Al oxide nanocluster formation in bcc Fe | Ab initio simulations carried out in different atomic cluster configurations
in bcc Fe matrix containing Zr and Al suggest energetic favorability of Y-Zr-O
phase nucleation, preferably with trigonal Y4Zr3O12 structure. Subsequently,
the HRTEM investigation of the as-prepared Fe - 14 Cr-0.3 Y2O3 - 0.6 Zr - 4Al
oxide dispersion strengthened (ODS) alloy shows 78% of precipitates with
Y4Zr3O12 structure, thereby confirming the predictive power of ab initio
simulations on the secondary formation in multi-component alloys. | 2105.12963v2 |
2021-08-14 | Deformed Special Relativity using a Generalized 't Hooft-Nobbenhuis Complex Transformation | A generalized form of 't Hooft-Nobbenhuis Complex space-time Transformation
is applied on momentum space from which a new model of Deformed Special
Relavity at Planck Scale is proposed. The model suggests an energy-dependent
Planck's "constant" that vary in space and time and Quantum Mechanics as a
low-energy approximation of perhaps a more fundamental theory at Planck Scale. | 2108.06474v2 |
2021-09-06 | Deep Convolutional Generative Modeling for Artificial Microstructure Development of Aluminum-Silicon Alloy | Machine learning which is a sub-domain of an Artificial Intelligence which is
finding various applications in manufacturing and material science sectors. In
the present study, Deep Generative Modeling which a type of unsupervised
machine learning technique has been adapted for the constructing the artificial
microstructure of Aluminium-Silicon alloy. Deep Generative Adversarial Networks
has been used for developing the artificial microstructure of the given
microstructure image dataset. The results obtained showed that the developed
models had learnt to replicate the lining near the certain images of the
microstructures. | 2109.06635v1 |
2021-09-17 | Fabricacion de un magnetron sputtering para deposito de peliculas nanometricas magneticas | This paper presents the development of scientific instrumentation for the
fabrication of ferromagnetic thin films, by sputtering technique, for the use
of 2-inch-diameter targets. Thin films were deposited using Permalloy alloy
(Ni80Fe20) as ferromagnetic material at room temperature on Si (001)
substrates. The film thicknesses were measured with profilometry and a
deposition rate for this alloy of 16.2 nm/min was calculated. Scanning electron
microscopy showed a continuous film formation and a chemical composition
similar to the target | 2109.08649v1 |
2021-10-09 | The design of quaternary eutectic solder by machine learning | In this paper, we obtain a Sn-Bi-In-Pb quaternary near eutectic alloy
composition from machine learning model. The eutectic points and the alloy
composition were evaluated and continuously improved by experimental input. The
actual composition is near the result given by machine learning. We conclude
that the application of machine learning in solder design has shown the
potential to overcome the challenge in searching for the next generation
eutectic solders, which will have a broad impact on the industry. | 2110.04529v1 |
2022-09-23 | Microstructural Pattern Formation during Far-from-Equilibrium Alloy Solidification | We introduce a new phase-field formulation of rapid alloy solidification that
quantitatively incorporates nonequilibrium effects at the solid-liquid
interface over a very wide range of interface velocities. Simulations identify
a new dynamical instability of dendrite tip growth driven by solute trapping at
velocities approaching the absolute stability limit. They also reproduce the
formation of the widely observed banded microstructures, revealing how this
instability triggers transitions between dendritic and microsegregation-free
solidification. Predicted band spacings agree quantitatively with observations
in rapidly solidified Al-Cu thin films. | 2209.11352v2 |
2022-09-28 | Systematic development of polynomial machine learning potentials for metallic and alloy systems | Machine learning potentials (MLPs) developed from extensive datasets
constructed from density functional theory (DFT) calculations have become
increasingly appealing for many researchers. This paper presents a framework of
polynomial-based MLPs, called polynomial MLPs. The systematic development of
accurate and computationally efficient polynomial MLPs for many elemental and
binary alloy systems and their predictive powers for various properties are
also demonstrated. Consequently, many polynomial MLPs are available in a
repository website. The repository will help many scientists perform accurate
and efficient large-scale atomistic simulations and crystal structure searches. | 2209.13823v1 |
2022-10-03 | Extra electron reflections in concentrated alloys do not necessitate short-range order | In many concentrated alloys of current interest, the observation of diffuse
superlattice intensities by transmission electron microscopy has been
attributed to chemical short-range order. We briefly review these findings and
comment on the plausibility of widespread interpretations, noting the absence
of expected peaks, conflicts with theoretical predictions, and the possibility
of alternative explanations. | 2210.01277v2 |
2022-12-05 | Interaction models and configurational entropies of binary MoTa and the MoNbTaW high entropy alloy | We introduce a simplified method to model the interatomic interactions of
high entropy alloys based on a lookup table of cluster energies. These
interactions are employed in replica exchange Monte Carlo simulations with
histogram analysis to obtain thermodynamic properties across a broad
temperature range. Kikuchi's Cluster Variation Method entropy formalism and
high temperature series expansions are applied to directly calculate entropy
from statistics on short- and long-range chemical order, and we discuss the
convergence of the entropy as clusters of differing size are included. | 2212.02470v1 |
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