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6,600 | Electronic Structure of Single- and Multiple-shell Carbon Fullerenes | cond-mat.mtrl-sci | We study the electronic states of giant single-shell and the recently
discovered nested multi-shell carbon fullerenes within the tight-binding
approximation. We use two different approaches, one based on iterations and the
other on symmetry, to obtain the $\pi$-state energy spectra of large fullerene
cages: $C_{240}$, ... | physics |
6,601 | Recursion and Path-Integral Approaches to the Analytic Study of the Electronic Properties of $C_{60}$ | cond-mat.mtrl-sci | The recursion and path-integral methods are applied to analytically study the
electronic structure of a neutral $C_{60}$ molecule. We employ a tight-binding
Hamiltonian which considers both the $s$ and $p$ valence electrons of carbon.
From the recursion method, we obtain closed-form {\it analytic} expressions for
the $... | physics |
6,602 | Phonon Transmission Rate, Fluctuations, and Localization in Random Semiconductor Superlattices: Green's Function Approach | cond-mat.mtrl-sci | We analytically study phonon transmission and localization in random
superlattices by using a Green's function approach. We derive expressions for
the average transmission rate and localization length, or Lyapunov exponent, in
terms of the superlattice structure factor. This is done by considering the
backscattering of... | physics |
6,603 | Phonon Universal Transmission Fluctuations and Localization in Semiconductor Superlattices with a Controlled Degree of Order | cond-mat.mtrl-sci | We study both analytically and numerically phonon transmission fluctuations
and localization in partially ordered superlattices with correlations among
neighboring layers. In order to generate a sequence of layers with a varying
degree of order we employ a model proposed by Hendricks and Teller as well as
partially ord... | physics |
6,604 | The effect of monomer evaporation on a simple model of submonolayer growth | cond-mat.mtrl-sci | We present a model for thin film growth by particle deposition that takes
into account the possible evaporation of the particles deposited on the
surface. Our model focuses on the formation of two-dimensional structures. We
find that the presence of evaporation can dramatically affect the growth
kinetics of the film, a... | physics |
6,605 | Statistical Mechanics of Cracks: Thermodynamic Limit, Fluctuations, Breakdown, and Asymptotics of Elastic Theory | cond-mat.mtrl-sci | We study a class of models for brittle fracture: elastic theory models which
allow for cracks but not for plastic flow. We show that these models exhibit,
at all finite temperatures, a transition to fracture under applied load similar
to that at a first order liquid-gas transition. We study this transition at low
tempe... | physics |
6,606 | The structure and phase stability of CO adsorbates on Rh(110) | cond-mat.mtrl-sci | The structure of CO adsorbates on the Rh(110) surface is studied at full
coverage using first-principles techniques. The relative energies of different
adsorbate geometries are determined by means of accurate structure
optimizations. In agreement with experiments, we find that a p2mg(2x1) 2CO
structure is the most stab... | physics |
6,607 | Theoretical Analysis of STM Experiments at Rutile TiO_2 Surfaces | cond-mat.mtrl-sci | A first-principles atomic orbital-based electronic structure method is used
to investigate the low index surfaces of rutile Titanium Dioxide. The method is
relatively cheap in computational terms, making it attractive for the study of
oxide surfaces, many of which undergo large reconstructions, and may be
governed by t... | physics |
6,608 | Improved Magnetic Information Storage using Return-Point Memory | cond-mat.mtrl-sci | The traditional magnetic storage mechanisms (both analog and digital) apply
an external field signal H(t) to a hysteretic magnetic material, and read the
remanent magnetization M(t), which is (roughly) proportional to H(t). We
propose a new analog method of recovering the signal from the magnetic
material, making use o... | physics |
6,609 | Zn-related deep centers in wurtzite GaN | cond-mat.mtrl-sci | Zn in GaN forms an efficient radiative center and acts as a deep acceptor
which can make the crystal insulating. Four different Zn-related centers have
been by now identified, leading to light emission in the range between 1.8 eV
and 2.9 eV. We present a first-principles investigation total energy and
electronic struct... | physics |
6,610 | Ab initio shallow acceptor levels in gallium nitride | cond-mat.mtrl-sci | Impurity levels and formation energies of acceptors in wurtzite GaN are
predicted ab initio. Be_Ga is found to be the shallow (thermal ionization
energy $\sim$ 0.06 eV); $Mg_{Ga}$ and $Zn_{Ga}$ are mid-deep acceptors (0.23 eV
and 0.33 eV respectively); $Ca_{Ga}$ and $Cd_{Ga}$ are deep acceptors
($\sim$0.65 eV); $Si_N$ ... | physics |
6,611 | Extracting convergent surface energies from slab calculations | cond-mat.mtrl-sci | The formation energy of a solid surface can be extracted from slab
calculations if the bulk energy per atom is known. It has been pointed out
previously that the resulting surface energy will diverge with slab thickness
if the bulk energy is in error, in the context of calculations which used
different methods to study... | physics |
6,612 | Characterization of the Noise in Secondary Ion Mass Spectrometry Depth Profiles | cond-mat.mtrl-sci | The noise in the depth profiles of secondary ion mass spectrometry (SIMS) is
studied using different samples under various experimental conditions. Despite
the noise contributions from various parts of the dynamic SIMS process, its
overall character agrees very well with the Poissonian rather than the Gaussian
distribu... | physics |
6,613 | Theoretical evidence for efficient p-type doping of GaN using beryllium | cond-mat.mtrl-sci | Ab initio calculations predict that Be is a shallow acceptor in GaN. Its
thermal ionization energy is 0.06 eV in wurtzite GaN; the level is valence
resonant in the zincblende phase. Be incorporation is severely limited by the
formation of Be_3N_2. We show however that co-incorporation with reactive
species can enhance ... | physics |
6,614 | Ab-initio study of oxygen vacancies in alpha-quartz | cond-mat.mtrl-sci | Extrinsic levels, formation energies, and relaxation geometries are
calculated ab initio for oxygen vacancies in alpha-quartz SiO2. The vacancy is
found to be thermodynamically stable in the charge states Q=+3, Q=0, Q=--2, and
Q=-3. The charged states are stabilized by large and asymmetric distortions
near the vacancy ... | physics |
6,615 | Fragmentation Phase Transition in Atomic Clusters II -----Symmetry of Fission of Metal Clusters---- | cond-mat.mtrl-sci | We present a statistical fragmentation study of doubly charged alkali (Li,
Na, K) and antimony clusters. The evaporation of one charged trimer is the most
dominant decay channel (asymmetric fission) at low excitation energies. For
small sodium clusters this was quite early found in molecular dynamical
calculations by L... | physics |
6,616 | Ab initio core-level shifts in metallic alloys | cond-mat.mtrl-sci | Core-level shifts and core-hole screening effects in alloy formation are
studied ``ab initio'' by constrained-density-functional total-energy
calculations. For our case study, the ordered intermetallic alloy MgAu,
final-state effects are essential to account for the experimental Mg 1s shift,
while they are negligible f... | physics |
6,617 | Pinning/depinning of crack fronts in heterogeneous materials | cond-mat.mtrl-sci | The fatigue fracture surfaces of a metallic alloy, and the stress corrosion
fracture surfaces of glass are investigated as a function of crack velocity. It
is shown that in both cases, there are two fracture regimes, which have a well
defined self-affine signature. At high enough length scales, the universal
roughness ... | physics |
6,618 | Phonon Softening and Elastic Instabilities in the Cubic-to-Orthorhombic Structural Transition of CsH | cond-mat.mtrl-sci | The cubic-to-orthorhombic structural transition occurring in CsH at a
pressure of about 17 GPa is studied by ab initio calculations. The relative
stability of the competing structures and the transition pressure are correctly
predicted. We show that this pressure-induced first-order transition is
intimately related to ... | physics |
6,619 | Invertible and Non-invertible Alloy Ising Models | cond-mat.mtrl-sci | Physical properties of alloys are compared as computed from ``direct'' and
``inverse'' procedures. The direct procedure involves Monte Carlo simulations
of a set of local density approximation (LDA)-derived pair and multibody
interactions {\nu_f}, generating short-range order (SRO), ground states, order-
disorder trans... | physics |
6,620 | The application of the M"obius inversion formula to the embedded-atom method | cond-mat.mtrl-sci | We present a systematical method for obtaining analytical long-range
embedded-atom potentials based on the lattice-inversion method. The potentials
converge faster (exponentially) than Sutton and Chen's power-law potentials
(Philos. Mag. Lett. 61, 2480(1990)). An interesting relationship between the
embedded-atom metho... | physics |
6,621 | Topology of amorphous tetrahedral semiconductors on intermediate lengthscales | cond-mat.mtrl-sci | Using the recently-proposed ``activation-relaxation technique'' for
optimizing complex structures, we develop a structural model appropriate to
a-GaAs which is almost free of odd-membered rings, i.e., wrong bonds, and
possesses an almost perfect coordination of four. The model is found to be
superior to structures obta... | physics |
6,622 | Local Entropy Characterization of Correlated Random Microstructures | cond-mat.mtrl-sci | A rigorous connection is established between the local porosity entropy
introduced by Boger et al. (Physica A 187, 55 (1992)) and the configurational
entropy of Andraud et al. (Physica A 207, 208 (1994)). These entropies were
introduced as morphological descriptors derived from local volume fluctuations
in arbitrary co... | physics |
6,623 | Influence of electron correlations on ground-state properties of III-V semiconductors | cond-mat.mtrl-sci | Lattice constants and bulk moduli of eleven cubic III-V semiconductors are
calculated using an ab initio scheme. Correlation contributions of the valence
electrons, in particular, are determined using increments for localized bonds
and for pairs and triples of such bonds; individual increments, in turn, are
evaluated u... | physics |
6,624 | Carbon superatom thin films | cond-mat.mtrl-sci | Assembling clusters on surfaces has emerged as a novel way to grow thin films
with targeted properties. In particular, it has been proposed from experimental
findings that fullerenes deposited on surfaces could give rise to thin films
retaining the bonding properties of the incident clusters. However the
microscopic st... | physics |
6,625 | Ab-initio theory of NMR chemical shifts in solids and liquids | cond-mat.mtrl-sci | We present a theory for the ab-initio computation of NMR chemical shifts
(sigma) in condensed matter systems, using periodic boundary conditions. Our
approach can be applied to periodic systems such as crystals, surfaces, or
polymers and, with a super-cell technique, to non-periodic systems such as
amorphous materials,... | physics |
6,626 | Effects of Small Island Mobility on Growth in Molecular Beam Epitaxy | cond-mat.mtrl-sci | The effects of mobility of small islands on island growth in molecular beam
epitaxy are studied. It is shown that small island mobility affects both the
scaling and morphology of islands during growth. Three microscopic models are
considered, in which the critical island sizes are $i^*=1,2$ and 3 (such that
islands of ... | physics |
6,627 | Models for diffusion and island growth in metal monolayers | cond-mat.mtrl-sci | A model that describes self diffusion, island nucleation and film growth on
FCC(001) metal substrates is presented. The parameters of the model are
optimized to describe Cu diffusion on Cu(001), by comparing activation energy
barriers to a full set of barriers obtained from semi-empirical potentials via
the embedded at... | physics |
6,628 | An Einstein Model of Brittle Crack Propagation | cond-mat.mtrl-sci | We propose a minimal nonlinear model of brittle crack propagation by
considering only the motion of the crack-tip atom. The model captures many
essential features of steady-state crack velocity and is in excellent
quantitative agreement with many-body dynamical simulations. The model exhibits
lattice-trapping. For load... | physics |
6,629 | On the Imbalance of the Dielectric Constant of the PbLixNb3xZr0.51Ti0.49-4xO3 Compound | cond-mat.mtrl-sci | In the present paper, the dielectric behaviour of the
PbLixNb3xZr0.51Ti0.49-4xO3 ( PLNZT) system is analyzed. It is shown that the
decrease in the dielectric constant with respect to an increase of the impurity
content may be due to an aggregation trend of the interacting off-centre
dipoles rather than due to cooperati... | physics |
6,630 | Finite Sized Atomistic Simulations of Screw Dislocations | cond-mat.mtrl-sci | The interaction of screw dislocations with an applied stress is studied using
atomistic simulations in conjunction with a continuum treatment of the role
played by the far field boundary condition. A finite cell of atoms is used to
consider the response of dislocations to an applied stress and this introduces
an additi... | physics |
6,631 | A Non-Local Formulation of the Peierls Dislocation Model | cond-mat.mtrl-sci | Cohesive zone models provide an illuminating and tractable way to include
constitutive nonlinearity into continuum models of defects. Powerful insights
have been gained by studying both dislocations and cracks using such analyses.
Recent work has shown that as a result of the locality assumption present in
such cohesiv... | physics |
6,632 | Extended Si defects | cond-mat.mtrl-sci | We perform total energy calculations based on the tight-binding Hamiltonian
scheme (i) to study the structural properties and energetics of the extended
{311} defects depending upon their dimensions and interstitial concentrations
and (ii) to find possible mechanisms of interstitial capture by and release
from the {311... | physics |
6,633 | First-Principles Wannier Functions of Silicon and Gallium Arsenide | cond-mat.mtrl-sci | We present a self-consistent, real-space calculation of the Wannier functions
of Si and GaAs within density functional theory. We minimize the total energy
functional with respect to orbitals which behave as Wannier functions under
crystal translations and, at the minimum, are orthogonal. The Wannier functions
are used... | physics |
6,634 | Mobility of dislocations in semiconductors | cond-mat.mtrl-sci | Atomic-scale calculations for the dynamics of the 90$^0$ partial glide
dislocation in silicon are made using the effective-medium tight-binding
theory. Kink formation and migration energies for the reconstructed partial
dislocation are compared with experimental results for the mobility of this
dislocation. The results... | physics |
6,635 | Membranes in rod solutions: a system with spontaneously broken symmetry | cond-mat.mtrl-sci | We consider a dilute solution of infinitely rigid rods near a curved,
perfectly repulsive surface and study the contribution of the rod depletion
layer to the bending elastic constants of membranes. We find that a spontaneous
curvature state can be induced by exposure of BOTH sides of the membrane to a
rod solution. A ... | physics |
6,636 | Magnetic Oscillations and Maxwell Theory | cond-mat.mtrl-sci | We explore the possibility of using the Kaluza-Klein geometry of Riemannian
Submersions to modify the classical Maxwell Theory. We further argue that the
resulting modification of Electromagnetism may be interesting in the context
of, among other topics, magnetic oscillations in metals. | physics |
6,637 | Mechanism of efficient carbon monoxide oxidation at Ru(0001) | cond-mat.mtrl-sci | We performed density-functional theory calculations using the generalized
gradient approximation for the exhange-correlation functional to investigate
the unusual catalytic behavior of Ru under elevated gas pressure conditions for
the carbon monoxide oxidation reaction, which includes a particularly high CO_2
turnover.... | physics |
6,638 | Density Functional Theory of Polar Insulators | cond-mat.mtrl-sci | We examine the density-functional theory of macroscopic insulators, obtained
in the large-cluster limit or under periodic boundary conditions. For polar
crystals, we find that the two procedures are not equivalent. In a
large-cluster case, the exact exchange-correlation potential acquires a
homogeneous ``electric field... | physics |
6,639 | The Equilibrium Shape of Quantum Dots | cond-mat.mtrl-sci | The formation of dislocation-free three-dimensional islands during the
heteroepitaxial growth of lattice-mismatched materials has been observed
experimentally for several material systems. The equilibrium shape of the
islands is governed by the competition between the surface energy and the
elastic relaxation energy of... | physics |
6,640 | Ab initio study of step formation and self-diffusion on Ag(100) | cond-mat.mtrl-sci | Using the plane wave pseudopotential method we performed density functional
theory calculations on the stability of steps and self-diffusion processes on
Ag(100). Our calculated step formation energies show that the {111}-faceted
step is more stable than the {110}-faceted step. In accordance with
experimental observati... | physics |
6,641 | The Adsorption of Atomic Nitrogen on Ru(0001): Geometry and Energetics | cond-mat.mtrl-sci | The local adsorption geometries of the (2x2)-N and the (sqrt(3)x
sqrt(3))R30^o -N phases on the Ru(0001) surface are determined by analyzing
low-energy electron diffraction (LEED) intensity data. For both phases,
nitrogen occupies the threefold hcp site. The nitrogen sinks deeply into the
top Ru layer resulting in a N-... | physics |
6,642 | Theory of self-diffusion in GaAs | cond-mat.mtrl-sci | Ab initio molecular dynamics simulations are employed to investigate the
dominant migration mechanism of the gallium vacancy in gaas as well as to
assess its free energy of formation and the rate constant of gallium
self-diffusion. our analysis suggests that the vacancy migrates by second
nearest neighbour hops. the ca... | physics |
6,643 | Morphology and thermal conductivity of model organic aerogels | cond-mat.mtrl-sci | The intersection volume of two independent 2-level cut Gaussian random fields
is proposed to model the open-cell microstructure of organic aerogels. The
experimentally measured X-ray scattering intensity, surface area and solid
thermal conductivity of both polymeric and colloidal organic aerogels can be
accounted for b... | physics |
6,644 | Electronic structure and band gap composition-dependence of the II-VI quaternary alloys | cond-mat.mtrl-sci | Based on a successful description of II-VI ternary alloys, which introduces
an empirical bowing parameter to the widely used virtual crystal approximation,
we set up a tight-binding Hamiltonian to describe the Zn_{1-y}Cd_ySe_{1-x}Te_x
and Zn_{.9}Cd_{.1}S_{.07}Se_{.93} quaternary alloys. We just use a formula that
can b... | physics |
6,645 | Orthorhombic Phase of Crystalline Polyethylene: A Monte Carlo Study | cond-mat.mtrl-sci | In this paper we present a classical Monte Carlo simulation of the
orthorhombic phase of crystalline polyethylene, using an explicit atom force
field with unconstrained bond lengths and angles and periodic boundary
conditions. We used a recently developed algorithm which apart from standard
Metropolis local moves emplo... | physics |
6,646 | Offsets and polarization at strained AlN/GaN polar interfaces | cond-mat.mtrl-sci | The strain induced by lattice mismatch at the interface is responsible for
the different value of the band discontinuities observed recently for the
AlN/GaN (AlN on GaN) and the GaN/AlN (GaN on AlN) polar (0001) interface. We
present a first-principles calculation of valence band offsets, interface
dipoles, strain-indu... | physics |
6,647 | Strong to fragile transition in a model of liquid silica | cond-mat.mtrl-sci | The transport properties of an ionic model for liquid silica at high
temperatures and pressure are investigated using molecular dynamics
simulations. With increasing pressure, a clear change from "strong" to
"fragile" behaviour (according to Angell's classification of glass-forming
liquids) is observed, albeit only on ... | physics |
6,648 | Numerical Solutions of the von Karman Equations for a Thin Plate | cond-mat.mtrl-sci | In this paper, we present an algorithm for the solution of the von Karman
equations of elasticity theory and related problems. Our method of successive
reconditioning is able to avoid convergence problems at any ratio of the
nonlinear streching and the pure bending energies. We illustrate the power of
the method by num... | physics |
6,649 | Calculation of Elastic Green's Functions for Lattices with Cavities | cond-mat.mtrl-sci | In this Brief Report, we present an algorithm for calculating the elastic
Lattice Greens Function of a regular lattice, in which defects are created by
removing lattice points. The method is computationally efficient, since the
required matrix operations are on matrices that scale with the size of the
defect subspace, ... | physics |
6,650 | Exchange Anisotropy in Epitaxial and Polycrystalline NiO/NiFe Bilayers | cond-mat.mtrl-sci | (001) oriented NiO/NiFe bilayers were grown on single crystal MgO (001)
substrates by ion beam sputtering in order to determine the effect that the
crystalline orientation of the NiO antiferromagnetic layer has on the
magnetization curve of the NiFe ferromagnetic layer. Simple models predict no
exchange anisotropy for ... | physics |
6,651 | Ion-Induced Surface Diffusion in Ion Sputtering | cond-mat.mtrl-sci | Ion bombardment is known to enhance surface diffusion and affect the surface
morphology. To quantify this phenomenon we calculate the ion-induced diffusion
constant and its dependence on the ion energy, flux and angle of incidence. We
find that ion bombardment can both enhance and suppress diffusion and that the
sign o... | physics |
6,652 | A correlated ab initio treatment of the zinc-blende wurtzite polytypism of SiC and III-V nitrides | cond-mat.mtrl-sci | Ground state properties of SiC, AlN, GaN and InN in the zinc-blende and
wurtzite structures are determined using an ab initio scheme. For the
self-consistent field part of the calculations, the Hartree-Fock program
Crystal has been used. Correlation contributions are evaluated using the
coupled-cluster approach with si... | physics |
6,653 | Circles, Spheres and Drops Packings | cond-mat.mtrl-sci | We studied the geometrical and topological rules underlying the dispositions
and the size distribution of non-overlapping, polydisperse circle-packings. We
found that the size distribution of circles that densely cover a plane follows
the power law: $N(R) \propto R^{-\alpha}$. We obtained an approximate
expression whic... | physics |
6,654 | Dynamical-charge neutrality at a crystal surface | cond-mat.mtrl-sci | For both molecules and periodic solids, the ionic dynamical charge tensors
which govern the infrared activity are known to obey a dynamical neutrality
condition. This condition enforces their sum to vanish (over the whole finite
system, or over the crystal cell, respectively). We extend this sum rule to the
non trivial... | physics |
6,655 | Ni-Au: A testing ground for theories of phase stability | cond-mat.mtrl-sci | The theory of phase stability in the Ni-Au alloy system is a popular topic
due to the large size mismatch between Ni and Au, which makes the effects of
atomic relaxation critical, and also the fact that Ni-Au exhibits a phase
separation tendency at low temperatures, but measurements at high-temperature
show an ordering... | physics |
6,656 | Effects of epitaxial strain and ordering direction on the electronic properties of (GaSb)_1/(InSb)_1 and (InAs)_1/(InSb)_1 superlattices | cond-mat.mtrl-sci | The structural and electronic properties in common anion (GaSb)_1/(InSb)_1
and common cation (InAs)_1/(InSb)_1 [111] ordered superlattices have been
determined using the local density total energy full potential linearized
augmented plane wave method. The influence of the ordering direction, strain
conditions and atomi... | physics |
6,657 | Influence of growth direction and strain conditions on the band line-up at GaSb/InSb and InAs/InSb interfaces | cond-mat.mtrl-sci | First-principles full potential linearized augmented plane wave (FLAPW)
calculations have been performed for lattice-mismatched common-atom III-V
interfaces. In particular, we have examined the effects of epitaxial strain and
ordering direction on the valence band offset in [001] and [111] GaSb/InSb and
InAs/InSb super... | physics |
6,658 | Electric fields and valence band offsets at strained [111] heterojunctions | cond-mat.mtrl-sci | [111] ordered common atom strained layer superlattices (in particular the
common anion GaSb/InSb system and the common cation InAs/InSb system) are
investigated using the ab initio full potential linearized augmented plane wave
(FLAPW) method. We have focused our attention on the potential line-up at the
two sides of t... | physics |
6,659 | Strain-Dependence of Surface Diffusion: Ag on Ag(111) and Pt(111) | cond-mat.mtrl-sci | Using density-functional theory with the local-density approximation and the
generalized gradient approximation we compute the energy barriers for surface
diffusion for Ag on Pt(111), Ag on one monolayer of Ag on Pt(111), and Ag on
Ag(111). The diffusion barrier for Ag on Ag(111) is found to increase linearly
with incr... | physics |
6,660 | Anomalous Behavior of Ru for Catalytic Oxidation: A Theoretical Study of the Catalytic Reaction CO + 1/2 O_2 --> CO_2 | cond-mat.mtrl-sci | Recent experiments revealed an anomalous dependence of carbon monoxide
oxidation at Ru(0001) on oxygen pressure and a particularly high reaction rate.
Below we report density functional theory calculations of the energetics and
reaction pathways of the speculated mechanism. We will show that the
exceptionally high rate... | physics |
6,661 | Surface relaxation and ferromagnetism of Rh(001) | cond-mat.mtrl-sci | The significant discrepancy between first-principles calculations and
experimental analyses for the relaxation of the (001) surface of rhodium has
been a puzzle for some years. In this paper we present density functional
theory calculations using the local-density approximation and the generalized
gradient approximatio... | physics |
6,662 | Adlayer core-level shifts of random metal overlayers on transition-metal substrates | cond-mat.mtrl-sci | We calculate the difference of the ionization energies of a core-electron of
a surface alloy, i.e., a B-atom in a A_(1-x) B_x overlayer on a
fcc-B(001)-substrate, and a core-electron of the clean fcc-B(001) surface using
density-functional-theory. We analyze the initial-state contributions and the
screening effects ind... | physics |
6,663 | Density-Functional Theory of Surface Diffusion and Epitaxial Growth of Metals | cond-mat.mtrl-sci | This paper gives a summary of basic concepts of density-functional theory
(DFT) and its use in state-of-the-art computations of complex processes in
condensed matter physics and materials science. In particular we discuss how
microscopic growth parameters can be determined by DFT and how on this basis
macroscopic pheno... | physics |
6,664 | Structural, electronic, and dynamical properties of amorphous gallium arsenide: a comparison between two topological models | cond-mat.mtrl-sci | We present a detailed study of the effect of local chemical ordering on the
structural, electronic, and dynamical properties of amorphous gallium arsenide.
Using the recently-proposed ``activation-relaxation technique'' and empirical
potentials, we have constructed two 216-atom tetrahedral continuous random
networks wi... | physics |
6,665 | Non-Nominal Value of the Dynamical Effective Charge in Alkaline-Earth Oxides | cond-mat.mtrl-sci | We calculate ab-initio the electronic states and the Born dynamical charge Z*
of the alkaline-earth oxides in the local-density approximation. We investigate
the trend of increasing Z* values through the series, using band-by-band
decompositions and computational experiments performed on fake materials with
artificiall... | physics |
6,666 | The role of zero-point effects in catalytic reactions involving hydrogen | cond-mat.mtrl-sci | According to the Heisenberg uncertainty principle of quantum mechanics,
particles which are localized in space by a bounding potential must have a
finite distribution of momenta. This leads, even in the lowest-possible energy
state, to vibrations, and thus, to the so-called zero-point energy. For
chemically bound hydro... | physics |
6,667 | Ab-initio study of BaTiO3 surfaces | cond-mat.mtrl-sci | We have carried out first-principles total-energy calculations of (001)
surfaces of the tetragonal and cubic phases of BaTiO3. Both BaO-terminated
(type I) and TiO2-terminated (type II) surfaces are considered, and the atomic
configurations have been fully relaxed. We found no deep-gap surface states for
any of the sur... | physics |
6,668 | First-principles theory of structural phase transitions for perovskites: competing instabilities | cond-mat.mtrl-sci | We extend our previous first-principles theory for perovskite ferroelectric
phase transitions to treat also antiferrodistortive phase transitions. Our
approach involves construction of a model Hamiltonian from a Taylor expansion,
first-principles calculations to determine expansion parameters, and Monte
Carlo simulatio... | physics |
6,669 | Formation of localized hole states in complex oxides | cond-mat.mtrl-sci | Defect electrons (holes) play an important role in most technologically
important complex oxides; many of which possess perovskite-related structures.
In this contribution we present the first detailed characterization of
localized hole states in such materials. Our investigations employ advanced
embedded-cluster calcu... | physics |
6,670 | Comment on "Structure and Hyperfine Parameters of E' Centers in alpha-quartz and Vitreous SiO2" | cond-mat.mtrl-sci | We point out that contrary to a recent suggestion by Boero et al. (PRL 78,
887 (1997)) the +1 charge state of the oxygen vacancy in alpha-quartz cannot be
invoked as a candidate E' center in alpha-quartz and silica. | physics |
6,671 | Evidence for Kondo Effect in Au80Co20 Ribbons | cond-mat.mtrl-sci | A minimum in resistivity as a function of temperature for an as-quenched
Au80Co20 ribbon prepared by melt-spinning using a wheel surface speed of 20 m
s^{-1} is found at 25 K. No resistivity minimum is found for an as-quenched
ribbon using a wheel surface speed of 60 m s^{-1}, however, upon heat treatment
of this ribbo... | physics |
6,672 | Semiempirical Hartree-Fock calculations for pure and Li-doped KTaO3 | cond-mat.mtrl-sci | In extension of our previous study of KNbO_3 by the semiempirical
Hartree-Fock method we present parameterization and total-energy results for
non-ferroelectric KTaO_3 as a pure crystal (concentrating on the frozen phonon
calculations) and that with Li impurities. The magnitudes of off-center Li
displacements and the r... | physics |
6,673 | Multiple small angle neutron scattering in ferromagnets | cond-mat.mtrl-sci | The conclusions arising from the multiple small angle neutron scattering
theory, developed recently by S.V. Maleyev, R.V. Pomortsev and Y.N. Skryabin
[Phys. Rev. B 50 7133 (1994)] for the value of Born parameter more than 1, are
experimentally confirmed by magnetic scattering from domain structure of pure
Fe and Ni, as... | physics |
6,674 | Solid molecular hydrogen: The Broken Symmetry Phase | cond-mat.mtrl-sci | By performing constant-pressure variable-cell ab initio molecular dynamics
simulations we find a quadrupolar orthorhombic structure, of $Pca2_1$ symmetry,
for the broken symmetry phase (phase II) of solid H2 at T=0 and P =110 - 150
GPa. We present results for the equation of state, lattice parameters and
vibronic frequ... | physics |
6,675 | X-ray absorption and resonant inelastic x-ray scattering in the rare earths | cond-mat.mtrl-sci | This paper makes a comparison between x-ray absorption (XAS) and resonant
inelastic x-ray scattering (RIXS) in the rare earths. Atomic calculations are
given for 2p -> 4f and 2p -> 5d XAS. The latter calculation includes the
contraction and expansion of the 5d orbitals resulting from the complete
exchange interaction w... | physics |
6,676 | Ensemble density-functional theory for ab-initio molecular dynamics of metals and finite-temperature insulators | cond-mat.mtrl-sci | A new method is presented for performing first-principles molecular-dynamics
simulations of systems with variable occupancies. We adopt a matrix
representation for the one-particle statistical operator Gamma, to introduce a
``projected'' free energy functional G that depends on the Kohn-Sham orbitals
only and that is i... | physics |
6,677 | Melting, freezing, and coalescence of gold nanoclusters | cond-mat.mtrl-sci | We present a detailed molecular-dynamics study of the melting, freezing, and
coalescence of gold nanoclusters within the framework of the embedded-atom
method. Concerning melting, we find the process to first affect the surface
(``premelting''), then to proceed inwards. The curve for the melting
temperature vs cluster ... | physics |
6,678 | Can liquid metal surfaces have hexatic order? | cond-mat.mtrl-sci | We propose that extended orientational correlations can appear at the surface
of supercooled heavy noble liquid metals, due to the same compressive forces
that cause reconstruction of their crystal surfaces. Simulations for liquid Au
show a packed surface layer structurally akin to a defected 2D triangular
solid. Upon ... | physics |
6,679 | Thermodynamically Stable One-Component Metallic Quasicrystals | cond-mat.mtrl-sci | Classical density-functional theory is employed to study finite-temperature
trends in the relative stabilities of one-component quasicrystals interacting
via effective metallic pair potentials derived from pseudopotential theory.
Comparing the free energies of several periodic crystals and rational
approximant models o... | physics |
6,680 | Fast diffusion of a Lennard-Jones cluster on a crystalline surface | cond-mat.mtrl-sci | We present a Molecular Dynamics study of large Lennard-Jones clusters
evolving on a crystalline surface. The static and the dynamic properties of the
cluster are described. We find that large clusters can diffuse rapidly, as
experimentally observed. The role of the mismatch between the lattice
parameters of the cluster... | physics |
6,681 | A Quantum Chemical Approach to Cohesive Properties of NiO | cond-mat.mtrl-sci | We apply ab-initio quantum chemical methods to calculate correlation effects
on cohesive properties of NiO, thereby extending a recently proposed scheme to
transition metal oxides with partially filled $d$-bands. We obtain good
agreement with experiment for the cohesive energy and show that the deviation
of the lattice... | physics |
6,682 | Ab Initio Linear Response Study of SrTiO3 | cond-mat.mtrl-sci | The lattice instabilities of perovskite structure oxides are responsible for
many of their interesting properties, such as temperature-dependent
ferroelectric phase transitions. First-principles calculations using linear
response theory provide an accurate means to determine the lattice dynamics
throughout the entire B... | physics |
6,683 | Self-diffusion of adatoms, dimers, and vacancies on Cu(100) | cond-mat.mtrl-sci | We use ab initio static relaxation methods and semi-empirical
molecular-dynamics simulations to investigate the energetics and dynamics of
the diffusion of adatoms, dimers, and vacancies on Cu(100). It is found that
the dynamical energy barriers for diffusion are well approximated by the
static, 0 K barriers and that p... | physics |
6,684 | Thermodynamically Stable One-Component Quasicrystals: A Density-Functional Survey of Relative Stabilities | cond-mat.mtrl-sci | A combination of classical density-functional theory and thermodynamic
perturbation theory is applied to a survey of finite-temperature trends in the
relative stabilities of one-component crystals and quasicrystals interacting
via effective metallic pair potentials derived from pseudopotential theory.
Comparing the fre... | physics |
6,685 | Normalization factors for magnetic relaxation of small particle systems in non-zero magnetic field | cond-mat.mtrl-sci | We critically discuss relaxation experiments in magnetic systems that can be
characterized in terms of an energy barrier distribution, showing that proper
normalization of the relaxation data is needed whenever curves corresponding to
different temperatures are to be compared. We show how these normalization
factors ca... | physics |
6,686 | Ewald methods for polarizable surfaces with application to hydroxylation and hydrogen bonding on the (012) and (001) surfaces of alpha-Fe2O3 | cond-mat.mtrl-sci | We present a clear and rigorous derivation of the Ewald-like method for
calculation of the electrostatic energy of the systems infinitely periodic in
two-dimensions and of finite size in the third dimension (slabs) which is
significantly faster than existing methods. Molecular dynamics simulations
using the transferabl... | physics |
6,687 | A period-doubled structure for the 90-degree partial dislocation in silicon | cond-mat.mtrl-sci | We suggest that the commonly-accepted core structure of the 90-degree partial
dislocation in Si may not be correct, and propose instead a period-doubled
structure. We present LDA, tight-binding, and classical Keating-model
calculations, all of which indicate that the period-doubled structure is lower
in energy. The new... | physics |
6,688 | Ab Initio Study of the Structural Phase Transition in Cubic Pb_3GeTe_4 | cond-mat.mtrl-sci | In the substitutionally disordered narrow-gap semiconductor Pb_{1-x}Ge_xTe, a
finite-temperature cubic-rhombohedral transition appears above a critical
concentration $x \approx 0.005$. As a first step towards a first-principles
investigation of this transition in the disordered system, a (hypothetical)
ordered cubic Pb... | physics |
6,689 | Environment Dependent Interatomic Potential for Bulk Silicon | cond-mat.mtrl-sci | We use recent theoretical advances to develop a new functional form for
interatomic forces in bulk silicon. The theoretical results underlying the
model include a novel analysis of elastic properties for the diamond and
graphitic structures and inversions of ab initio cohesive energy curves. The
interaction model inclu... | physics |
6,690 | The effects of interface morphology on Schottky barrier heights: a case study on Al/GaAs(001) | cond-mat.mtrl-sci | The problem of Fermi-level pinning at semiconductor-metal contacts is
readdressed starting from first-principles calculations for Al/GaAs. We give
quantitative evidence that the Schottky barrier height is very little affected
by any structural distortions on the metal side---including elongations of the
metal-semicondu... | physics |
6,691 | Predicion of charge separation in GaAs/AlAs cylindrical Russian Doll nanostructures | cond-mat.mtrl-sci | We have contrasted the quantum confinement of (i) multiple quantum wells of
flat GaAs and AlAs layers, i.e. $(\GaAs)_{m}/(\AlAs)_n/(\GaAs)_p/(\AlAs)_q$,
with (ii) ``cylindrical Russian Dolls'' -- an equivalent sequence of wells and
barriers arranged as concentric wires. Using a pseudopotential plane-wave
calculation, w... | physics |
6,692 | Theoretical examination of stress fields in Pb(Zr_0.5Ti_0.5)O_3 | cond-mat.mtrl-sci | In this paper, we develop a rigorous formulation of the local stress field.
This approach can be used in conjuction with any first-principles method to
study stress fields in complex bonded systems. In particular we investigate the
induced stress fields resulting from homogeneous deformations for tetragonal
PbTiO_3 and... | physics |
6,693 | Calculated thermoelectric properties of La-filled skutterudites | cond-mat.mtrl-sci | The thermoelectric properties of La-filled skutterudites are discussed from
the point of view of their electronic structures. These are calculated from
first principles within the local density approximation. The electronic
structure is in turn used to determine transport related quantities. Virtual
crystal calculation... | physics |
6,694 | Ab initio Quantum and ab initio Molecular Dynamics of the Dissociative Adsorption of Hydrogen on Pd(100) | cond-mat.mtrl-sci | The dissociative adsorption of hydrogen on Pd(100) has been studied by ab
initio quantum dynamics and ab initio molecular dynamics calculations. Treating
all hydrogen degrees of freedom as dynamical coordinates implies a high
dimensionality and requires statistical averages over thousands of
trajectories. An efficient ... | physics |
6,695 | Spontaneous polarization and piezoelectric constants of III-V nitrides | cond-mat.mtrl-sci | The spontaneous polarization, dynamical Born charges, and piezoelectric
constants of the III-V nitrides AlN, GaN, and InN are studied ab initio using
the Berry phase approach to polarization in solids. The piezoelectric constants
are found to be up 10 times larger than in conventional III-V's and II-VI's,
and comparabl... | physics |
6,696 | Effective medium theory of the optical properties of aligned carbon nanotubes | cond-mat.mtrl-sci | We present an effective medium theory in order to analyze the reported
optical properties of aligned carbon nanotube films (W.A. de Heer et al.,
Science 268, 845 (1995)). This methodology is based on photonic band structure
calculations and allows treatment of complex media consisting of particles that
interact strongl... | physics |
6,697 | First principles study of adsorbed Cu_n (n=1-4) microclusters on MgO(100): structural and electronic properties | cond-mat.mtrl-sci | We present a density functional study of the structural and electronic
properties of small Cu_n (n=1,4) aggregates on defect-free MgO(100). The
calculations employ a slab geometry with periodic boundary conditions,
supercells with up to 76 atoms, and include full relaxation of the surface
layer and of all adsorbed atom... | physics |
6,698 | Refined Geometry and Frozen Phonons in KNbO3 | cond-mat.mtrl-sci | In order to arrive at ultimately accurate results available with the LMTO
method in the local density approximation, the stability of full-potential LMTO
predictions for off-center displacements in KNbO3, as depending on the choice
of basis and expansion cutoffs, has been thoroughly investigated. With the
calculation s... | physics |
6,699 | Surface reconstruction induced geometries of Si clusters | cond-mat.mtrl-sci | We discuss a generalization of the surface reconstruction arguments for the
structure of intermediate size Si clusters, which leads to model geometries for
the sizes 33, 39 (two isomers), 45 (two isomers), 49 (two isomers), 57 and 61
(two isomers). The common feature in all these models is a structure that
closely rese... | physics |
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