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8,700 | Time-Dependent Local Density Approximation for Collective Excitations of Atomic Clusters | physics.atm-clus | We discuss the calculation of collective excitations in atomic clusters using
the time-dependent local density approximation. In principle there are many
formulations of the TDLDA, but we have found that a particularly efficient
method for large clusters is to use a coordinate space mesh and the algorithms
for the oper... | physics |
8,701 | Nonradiative Electronic Deexcitation Time Scales in Metal Clusters | physics.atm-clus | The life-times due to Auger-electron emission for a hole on a deep electronic
shell of neutral and charged sodium clusters are studied for different sizes.
We consider spherical clusters and calculate the Auger-transition probabilities
using the energy levels and wave functions calculated in the
Local-Density-Approxima... | physics |
8,702 | Oscillator strengths with pseudopotentials | physics.atm-clus | The time-dependent local-density approximation (TDLDA) is shown to remain
accurate in describing the atomic response of IB elements under the additional
approximation of using pseudopotentials to treat the effects of core electrons.
This extends the work of Zangwill and Soven who showed the utility of the
all-electron ... | physics |
8,703 | Cluster ionization via two-plasmon excitation | physics.atm-clus | We calculate the two-photon ionization of clusters for photon energies near
the surface plasmon resonance. The results are expressed in terms of the
ionization rate of a double plasmon excitation, which is calculated
perturbatively. For the conditions of the experiment by Schlipper et al., we
find an ionization rate of... | physics |
8,704 | Dissociative Autoionization in (1+2)-photon Above Threshold Excitation of H2 Molecules | physics.atm-clus | We have theoretically studied the effect of dissociative autoionization on
the photoelectron energy spectrum in (1+2)-photon above threshold
ionization(ATI) of H2 molecules. We have considered excitation from the ground
state X-singlet-Sigma-g+(v=0,j) to the doubly excited autoionizing states of
singlet-Sigma-u+ and si... | physics |
8,705 | Noncollinear magnetic ordering in small Chromium Clusters | physics.atm-clus | We investigate noncollinear effects in antiferromagnetically coupled clusters
using the general, rotationally invariant form of local spin-density theory.
The coupling to the electronic degrees of freedom is treated with relativistic
non-local pseudopotentials and the ionic structure is optimized by Monte-Carlo
techniq... | physics |
8,706 | Optical response of small silver clusters | physics.atm-clus | The time-dependent local density approximation is applied to the optical
response of the silver clusters, Ag_2, Ag_3, Ag_8 and Ag_9^+. The calculation
includes all the electrons beyond the closed-shell Ag^{+11} ionic core, thus
including for the first time explicitly the filled d-shell in the response. The
excitation e... | physics |
8,707 | Orbital Magnetic Dipole Mode in Deformed Clusters: A Fully Microscopic Analysis | physics.atm-clus | The orbital M1 collective mode predicted for deformed clusters in a schematic
model is studied in a self-consistent random-phase-approximation approach which
fully exploits the shell structure of the clusters. The microscopic mechanism
of the excitation is clarified and the close correlation with E2 mode
established. T... | physics |
8,708 | Quantum Monte Carlo study of the H- impurity in small helium clusters | physics.atm-clus | We report ground state energies and structural properties for small helium
clusters (4He) containing an H- impurity computed by means of variational and
diffusion Monte Carlo methods. Except for 4He_2H- that has a noticeable
contribution from collinear geometries where the H- impurity lies between the
two 4He atoms, ou... | physics |
8,709 | Tight-binding molecular dynamic study of silver clusters | physics.atm-clus | Tight-binding molecular dynamics (TBMD) is used to study the structural and
electronic properties of silver clusters. The ground state structures of Ag
clusters up to 21 atoms are optimized via TBMD combined with genetic algorithm
(GA). The detailed comparison with {\em ab initio} results on small Ag$_n$
clusters (n=3-... | physics |
8,710 | Photoelectron spectra of aluminum cluster anions: Temperature effects and ab initio simulations | physics.atm-clus | Photoelectron (PES) spectra from aluminum cluster anions (from 12 to 15
atoms) at various temperature regimes, were studied using ab-initio molecular
dynamics simulations and experimentally. The calculated PES spectra, obtained
via shifting of the simulated electronic densities of states by the
self-consistently determ... | physics |
8,711 | Structures and Stabilities of CaO and MgO Clusters and Cluster Ions: An alternative interpretation of the experimental mass spectra | physics.atm-clus | The structures and relative stabilities of doubly-charged nonstoichiometric
(CaO)$_n$Ca$^{2+}$ (n=1--29) cluster ions and of neutral stoichiometric
(MgO)$_n$ and (CaO)$_n$ (n=3,6,9,12,15,18) clusters are studied through {\em ab
initio} Perturbed Ion plus polarization calculations. The large
coordination-dependent polar... | physics |
8,712 | A transferable nonorthogonal tight-binding model of germanium: application to small clusters | physics.atm-clus | We have developed a transferable nonorthogonal tight-binding total energy
model for germanium and use it to study small clusters. The cohesive energy,
bulk modulus, elastic constants of bulk germanium can be described by this
model to considerably good extent. The calculated bulk phase diagram for
germanium agrees well... | physics |
8,713 | Melting behavior of large disordered sodium clusters | physics.atm-clus | The melting-like transition in disordered sodium clusters Na_N, with N=92 and
142 is studied by using a first-principles constant-energy molecular dynamics
simulation method. Na_142, whose atoms are distributed in two (surface and
inner) main shells with different radial distances to the center of mass of the
cluster, ... | physics |
8,714 | An orbital-free molecular dynamics study of melting in K_20, K_55, K_92, K_142, Rb_55 and Cs_55 clusters | physics.atm-clus | The melting-like transition in potasium clusters K_N, with N=20, 55, 92 and
142, is studied by using an orbital-free density-functional constant-energy
molecular dynamics simulation method, and compared to previous theoretical
results on the melting-like transition in sodium clusters of the same sizes.
Melting in potas... | physics |
8,715 | Emergence of Bulk CsCl Structure in (CsCl)nCs+ Cluster Ions | physics.atm-clus | The emergence of CsCl bulk structure in (CsCl)nCs+ cluster ions is
investigated using a mixed quantum-mechanical/semiempirical theoretical
approach. We find that rhombic dodecahedral fragments (with bulk CsCl symmetry)
are more stable than rock-salt fragments after the completion of the fifth
rhombic dodecahedral atomi... | physics |
8,716 | Orientational melting of two-shell carbon nanoparticles: molecular dynamics study | physics.atm-clus | The energetic characteristics of two-shell carbon nanoparticles ("onions")
with different shapes of second shell are calculated. The barriers of relative
rotation of shells are found to be surprisingly small; therefore, free relative
rotation of shells can take place at room temperature. The intershell
orientational me... | physics |
8,717 | Thermodynamics of Na_8 and Na_{20} clusters studied with ab-initio electronic structure methods | physics.atm-clus | We study the thermodynamics of Na_8 and Na_{20} clusters using
multiple-histogram methods and an ab initio treatment of the valence electrons
within density functional theory. We consider the influence of various electron
kinetic-energy functionals and pseudopotentials on the canonical ionic specific
heats. The results... | physics |
8,718 | Time dependent energy absorption of atomic clusters from an intense laser pulse | physics.atm-clus | For the energy absorption of atomic clusters as a function of the laser pulse
duration we find a similar behavior as it has been observed for metallic
clusters [K\"oller et al., Phys. Rev. Lett. {\bf 82}, 3783 (1999)]. In both
situations there exists an optimum radius $R_{o}$ of the cluster for energy
absorption. In th... | physics |
8,719 | Structure and Magnetism of Neutral and Anionic Palladium Clusters | physics.atm-clus | The properties of neutral and anionic Pd_N clusters were investigated with
spin-density-functional calculations. The ground state structures are
three-dimensional for N>3 and they are magnetic with a spin-triplet for 2<=N<=7
and a spin nonet for N=13 neutral clusters. Structural- and spin-isomers were
determined and an... | physics |
8,720 | Adsorption of CO on a Platinum (111) surface - a study within a four-component relativistic density functional approach | physics.atm-clus | We report on results of a theoretical study of the adsorption process of a
single carbon oxide molecule on a Platinum (111) surface. A four-component
relativistic density functional method was applied to account for a proper
description of the strong relativistic effects. A limited number of atoms in
the framework of a... | physics |
8,721 | C$_{60}$ in intense femtosecond laser pulses: nonlinear dipole response and ionization | physics.atm-clus | We study the interaction of strong femtosecond laser pulses with the C$_{60}$
molecule employing time-dependent density functional theory with the ionic
background treated in a jellium approximation. The laser intensities considered
are below the threshold of strong fragmentation but too high for perturbative
treatment... | physics |
8,722 | Robust wave function optimization procedures in quantum Monte Carlo methods | physics.atm-clus | The energy variance optimization algorithm over a fixed ensemble of
configurations in variational Monte Carlo is formally identical to a problem of
fitting data: we reexamine it from a statistical maximum-likelihood point of
view. We detect the origin of the problem of convergence that is often
encountered in practice ... | physics |
8,723 | Can optical spectroscopy directly elucidate the ground state of C20? | physics.atm-clus | The optical response of the lowest energy members of the C20 family is
calculated using time-dependent density functional theory within a real-space,
real-time scheme. Significant differences are found among the spectra of the
different isomers, and thus we propose optical spectroscopy as a tool for
experimental invest... | physics |
8,724 | New Approach to Nonlinear Dynamics of Fullerenes and Fullerites | physics.atm-clus | New type of nonlinear (anharmonic) excitations -- bushes of vibrational modes
-- in physical systems with point or space symmetry are discussed. All infrared
active and Raman active bushes for C60 fulerene are found by means of special
group-theoretical methods. | physics |
8,725 | Density functional study of Au$_n$ (n=2-20) clusters: lowest-energy structures and electronic properties | physics.atm-clus | We have investigated the lowest-energy structures and electronic properties
of the Au$_n$(n=2-20) clusters based on density functional theory (DFT) with
local density approximation. The small Au$_n$ clusters adopt planar structures
up to n=6. Tabular cage structures are preferred in the range of n=10-14 and a
structura... | physics |
8,726 | Mass spectrometric and first principles study of Al$_n$C$^-$ clusters | physics.atm-clus | We study the carbon-dope aluminum clusters by using time-of-flight mass
spectrum experiments and {\em ab initio} calculations. Mass abundance
distributions are obtained for anionic aluminum and aluminum-carbon mixed
clusters. Besides the well-known magic aluminum clusters such as Al$_{13}^-$
and Al$_{23}^-$, Al$_7$C$^-... | physics |
8,727 | Ground state and excitation dynamics in Ag doped helium clusters | physics.atm-clus | We present a quantum Monte Carlo study of the structure and energetics of
silver doped helium clusters AgHe$_n$ for $n$ up to 100. Our simulations show
the first solvation shell of the Ag atom to be composed by roughly 20 He atoms,
and to possess a structured angular distribution. Moreover, the electronic
$^2$P$_{1/2}\... | physics |
8,728 | Polarizabilities of germanium clusters | physics.atm-clus | Polarizabilities of Ge$_n$ clusters with 2 to 25 atoms are calculated using
coupled-perturbation Hartree-Fock (CPHF) and finite field (FF) method within
density functional theory. The polarizabilities of the Ge$_n$ clusters increase
rapidly in the size range of 2 to 5 atoms and then fluctuate around the bulk
value. The... | physics |
8,729 | Novel structures of Co-Cu bimetallic clusters and their magnetic properties | physics.atm-clus | The structural and magnetic properties of Co$_{18-m}$Cu$_m$ ($0\leq m\leq
18$) clusters are investigated with a genetic algorithm and a $spd$-band model
Hamiltonian in the unrestricted Hartree-Hock approximation respectively. In
general, Cu atoms tend to occupy the surface, while Co atoms prefer to the
interior of the ... | physics |
8,730 | Laser Spinning of Nanotubes: A path to fast-rotating microdevices | physics.atm-clus | We show that circularly polarized light can spin nanotubes with GHz
frequencies. In this method, angular moments of infrared photons are resonantly
transferred to nanotube phonons and passed to the tube body by "umklapp"
scattering. We investigate experimental realization of this ultrafast rotation
in carbon nanotubes,... | physics |
8,731 | Formalism for Multiphoton Plasmon Excitation in Jellium Clusters | physics.atm-clus | We present a new formalism for the description of multiphoton plasmon
excitation processes in jellium clusters. By using our method, we demonstrate
that, in addition to dipole plasmon excitations, the multipole plasmons
(quadrupole, octupole, etc) can be excited in a cluster by multiphoton
absorption processes, which r... | physics |
8,732 | Atomistic Simulations of Nanotube Fracture | physics.atm-clus | The fracture of carbon nanotubes is studied by atomistic simulations. The
fracture behavior is found to be almost independent of the separation energy
and to depend primarily on the inflection point in the interatomic potential.
The rangle of fracture strians compares well with experimental results, but
predicted range... | physics |
8,733 | Giant Magnetic Moments of Nitrogen Stabilized Mn Clusters and Their Relevance to Ferromagnetism in Mn Doped GaN | physics.atm-clus | Using first principles calculations based on density functional theory, we
show that the stability and magnetic properties of small Mn clusters can be
fundamentally altered by the presence of nitrogen. Not only are their binding
energies substantially enhanced, but also the coupling between the magnetic
moments at Mn s... | physics |
8,734 | Effects of Defects on the Strength of Nanotubes: Experimental-Computational Comparisons | physics.atm-clus | The failure stresses and strains of nanotubes given by theoretical or
numerical predictions are much higher than observed in experiments. We show
that defects can explain part of this discrepancy: for an n-atom defect with
2<=n<=8, the range of failure stresses for a molecular mechanics calculation is
found to be 36GPa... | physics |
8,735 | Intense pulsed helium droplet beams | physics.atm-clus | Pulsed (30 - 100 microseconds) nozzle beams have been used to generate helium
droplets (<N> = 10^4-10^5). The dependence of the beam intensity and the mean
droplet size on the source stagnation pressure and temperature are studied via
mass spectroscopy and laser induced fluorescence of embedded phthalocyanine
molecules... | physics |
8,736 | Ionization of clusters in strong X-ray laser pulses | physics.atm-clus | The effect of intense X-ray laser interaction on argon clusters is studied
theoretically with a mixed quantum/classical approach. In comparison to a
single atom we find that ionization of the cluster is suppressed, which is in
striking contrast to the observed behavior of rare-gas clusters in intense
optical laser puls... | physics |
8,737 | Enhanced ionization in small rare gas clusters | physics.atm-clus | A detailed theoretical investigation of rare gas atom clusters under intense
short laser pulses reveals that the mechanism of energy absorption is akin to
{\it enhanced ionization} first discovered for diatomic molecules. The
phenomenon is robust under changes of the atomic element (neon, argon, krypton,
xenon), the nu... | physics |
8,738 | Fringe Structure in the Phase-Space Dynamics of Atomic Stabilization in An Intense Field | physics.atm-clus | An analytical expression of a Floquet operator, which describes the evolution
of a wave packet in combined atomic and an intense laser field,is obtained
approximately in the stabilization regime. Both the classical and quantum
versions of the Floquet operator are used to study the phase-space dynamics of
atomic stabili... | physics |
8,739 | Revisiting the Complexity of Finding Globally Minimum Energy Configurations in Atomic Clusters | physics.atm-clus | It has previously been proven that finding the globally minimum energy
configuration of an atomic cluster belongs in the class of NP-hard problems.
However, this proof is limited only to homonuclear clusters. This paper
presents a new proof which shows finding minimum energy configurations for
heteronuclear clusters is... | physics |
8,740 | Cluster growing process and a sequence of magic numbers | physics.atm-clus | We present a new theoretical framework for modelling the cluster growing
process. Starting from the initial tetrahedral cluster configuration, adding
new atoms to the system and absorbing its energy at each step, we find cluster
growing paths up to the cluster sizes of more than 100 atoms. We demonstrate
that in this w... | physics |
8,741 | Work functions, ionization potentials, and in-between: Scaling relations based on the image charge model | physics.atm-clus | We revisit a model in which the ionization energy of a metal particle is
associated with the work done by the image charge force in moving the electron
from infinity to a small cut-off distance just outside the surface. We show
that this model can be compactly, and productively, employed to study the size
dependence of... | physics |
8,742 | Temperature-induced pair correlations in clusters and nuclei | physics.atm-clus | The pair correlations in mesoscopic systems such as $nm$-size superconducting
clusters and nuclei are studied at finite temperature for the canonical
ensemble of fermions in model spaces with a fixed particle number: i) a
degenerate spherical shell (strong coupling limit), ii) an equidistantly spaced
deformed shell (we... | physics |
8,743 | Study of interaction of high-power Ar$^+$ laser beam with Ag$^+$-doped glass | physics.atm-clus | In this work, we have investigated the interaction of a high-power Ar$^+$
laser beam, in a continuous multi-line regime, with Ag$^+$-doped glass samples.
The samples were subjected to the irradiation after the ion-exchange step. As a
result of the irradiation, a peak appears in the absorption spectrum; its
evolution de... | physics |
8,744 | Binding energy of the ^3He^4He_2 trimer within the hard-core Faddeev approach | physics.atm-clus | We apply a hard-core version of the Faddeev differential equations to the
^3He^4He_2 three-atomic system. Using these equations we calculate the binding
energy of the ^3He^4He_2 trimer with the LM2M2 potential by Aziz and Slaman and
more recent TTY potential by Tang, Toennies and Yiu. | physics |
8,745 | Linking Vibrational Dynamics to Local Electronic Structure: Local Analysis of Dynamics of the relaxed Si$_{87}$ Cluster | physics.atm-clus | A flexible scheme for decomposing the vibrational density of states in terms
of pair vibrational density of states is presented. This scheme provides the
linkage between the site vibrational density of states and pair vibrational
density of states so that vibrational modes, in particular localized modes, can
be conveni... | physics |
8,746 | Optimal representations of quantum states by gaussians in phase space | physics.atm-clus | A two-step optimization is proposed to represent an arbitrary quantum state
to a desired accuracy with the least number of gaussians in phase space. The
Husimi distribution of the quantum state provides the information to determine
the modulus of the weight for the gaussians. Then, the phase information
contained in th... | physics |
8,747 | Ab initio density functional investigation of B_24 cluster: Rings, Tubes, Planes, and Cages | physics.atm-clus | We investigate the equilibrium geometries and the systematics of bonding in
various isomers of a 24-atom boron cluster using Born-Oppenheimer molecular
dynamics within the framework of density functional theory. The isomers studied
are the rings, the convex and the quasiplanar structures, the tubes and, the
closed stru... | physics |
8,748 | Dynamics in a cluster under the influence of intense femtosecond hard x-ray pulses | physics.atm-clus | In this paper we examine the behavior of small cluster of atoms in a short
(10-50 fs) very intense hard x-ray (10 keV) pulse. We use numerical modeling
based on the non-relativistic classical equation of motion. Quantum processes
are taken into account by the respective cross sections. We show that there is
a Coulomb e... | physics |
8,749 | Molecular Dynamics Simulation of the Melting Behaviours of 12-, 13-, 14-Atom Icosahedral Platinum Clusters | physics.atm-clus | Using molecular dynamics simulation technique, we have studied the melting
behaviours of free, icosahedral PtN clusters in the size range of N=12-14.
Voter and Chen version of an embedded-atom model, derived by fitting to
experimental data of both diatomic molecule and bulk platinum simultaneously,
has been employed in... | physics |
8,750 | Low-energy quadrupole modes in deformed clusters | physics.atm-clus | Properties of low-energy (infra-red) quadrupole modes (LEQM) of multipolarity
$+AFw-lambda+AFw-mu =$20, 21 and 22 in deformed sodium clusters are studied
within the Kohn-Sham LDA RPA approach. Possible manifestations of LEQM in
stimulated Raman adiabatic passage (STIRAP) reaction are discussed. It is shown
that, in fre... | physics |
8,751 | Coulomb three-body systems and charge transfer collisions in a configuration-space approach | physics.atm-clus | Some low-energy three-body muon- and electron-transfer processes are
considered within the Faddeev-Hahn formulation using two-, six-, and ten-state
close-coupling approximation. We test our approach in bound-state problems for
systems H$_2^+$ and ($\mu^-$dd)$^+$ within six- and ten-state schemes, where
$d$ is a deutero... | physics |
8,752 | OCS in small para-hydrogen clusters: energetics and structure with N=1-8 complexed hydrogen molecules | physics.atm-clus | We determine the structure and energetics of complexes of the linear OCS
molecule with small numbers of para-hydrogen molecules, N=1-8, using zero
temperature quantum Monte Carlo methods. Ground state calculations are carried
out with importance-sampled rigid body diffusion Monte Carlo (IS-RBDMC) and
excited state calc... | physics |
8,753 | Evolution in the structural and bonding properties of Aluminum-Lithium clusters | physics.atm-clus | We present a systematic study of the geometries, energetics, electronic
structure and bonding in various Al-Li clusters viz. AlnLin ($n$=1-11),
Al$_2^-$, Al$_2^{2-}$, Al$_2$Li, Al$_2$Li$^-$, and Al6Li8 using
Born-Oppenheimer molecular dynamics within the framework of density functional
theory. The growth pattern in the... | physics |
8,754 | Microscopic study of the He2-SF6 trimers | physics.atm-clus | The He2-SF6 trimers, in their different He isotopic combinations, are studied
both in the framework of the correlated Jastrow approach and of the Correlated
Hyperspherical Harmonics expansion method. The energetics and structure of the
He-SF6 dimers are analyzed, and the existence of a characteristic rotational
band in... | physics |
8,755 | Close-Packing of Clusters: Application to Al_100 | physics.atm-clus | The lowest energy configurations of close-packed clusters up to N=110 atoms
with stacking faults are studied using the Monte Carlo method with Metropolis
algorithm. Two types of contact interactions, a pair-potential and a many-atom
interaction, are used. Enhanced stability is shown for N=12, 26, 38, 50, 59,
61, 68, 75... | physics |
8,756 | Ionization of clusters in intense laser pulses through collective electron dynamics | physics.atm-clus | The motion of electrons and ions in medium-sized rare gas clusters (1000
atoms) exposed to intense laser pulses is studied microscopically by means of
classical molecular dynamics using a hierarchical tree code. Pulse parameters
for optimum ionization are found to be wavelength dependent. This resonant
behavior is trac... | physics |
8,757 | Small rare gas clusters in soft X-ray pulses | physics.atm-clus | We develop a microscopic model for the interaction of small rare gas clusters
with soft X-ray radiation. It is shown that, while the overall charging of the
clusters is rather low, unexpectedly high atomic charge states can arise due to
charge imbalances inside the cluster. The mechanism does not require unusually
high... | physics |
8,758 | Structure and stability of copper clusters : A tight-binding molecular dynamics study | physics.atm-clus | In this paper we propose a tight-binding molecular dynamics with parameters
fitted to first-principles calculations on the smaller clusters and with an
environment correction, to be a powerful technique for studying large
transition/noble metal clusters. In particular, the structure and stability of
$Cu_n$ clusters for... | physics |
8,759 | Optical response of small magnesium clusters | physics.atm-clus | We predict the strong enhancement in the photoabsorption of small Mg clusters
in the region of 4-5 eV due to the resonant excitation of the plasmon
oscillations of cluster electrons. The photoabsorption spectra for neutral Mg
clusters consisting of up to N=11 atoms have been calculated using ab initio
framework based o... | physics |
8,760 | Can Small Free Methane Clusters Exhibit Phase-like Transitions? | physics.atm-clus | Low-temperature (below 60K) phase changes of free clusters containing 50,
137, and 229 methane molecules have been observed in isoenergetic Molecular
Dynamics computations. Bulk solid methane exhibits structural phase
transformation at 20.4 K. However, clusters of 50 molecules already melt at
about 25 K, which makes th... | physics |
8,761 | Why do gallium clusters have a higher melting point than the bulk? | physics.atm-clus | Density functional molecular dynamical simulations have been performed on
Ga$_{17}$ and Ga$_{13}$ clusters to understand the recently observed
higher-than-bulk melting temperatures in small gallium clusters [Breaux {\em et
al.}, Phys. Rev. Lett. {\bf 91}, 215508 (2003)]. The specific-heat curve,
calculated with the mul... | physics |
8,762 | Electron diffraction data on structural transformations in free clucters of argon | physics.atm-clus | An electron diffraction technique is used to study the structure of clusters
formed in an isentropically expanding supersonic argon jet. The formation of
the hcp phase with increasing cluster size is reliably detected for the first
time. Observations are made for mean cluster sizes N in the range from 1x10^3
to 8x10^4 ... | physics |
8,763 | Conformational properties of neutral and charged alanine and glycine chains | physics.atm-clus | We have investigated the potential energy surface for neutral and charged
alanine and glycine chains consisting of up to 6 amino acids. For these
molecules we have calculated potential energy surfaces as a function of the
Ramachandran angles phi and psi. Our calculations are performed within it ab
initio theoretical fr... | physics |
8,764 | Fission of charged alanine dipeptides | physics.atm-clus | In this work we have performed for the first time a systematic analysis of
the dissociation and fission pathways of neutral, singly and doubly charged
alanine dipeptide ions with the aim to identify the fission mechanism and the
most probable fragmentation channels of these type of molecules. We demonstrate
the importa... | physics |
8,765 | Electron--phonon coupling and anharmonic effects in metal clusters | physics.atm-clus | The periods of the harmonic oscillations of the ion core of charged sodium
clusters around the equilibrium shapes are considered. It is found that these
periods are of the order of magnitude of the experimentally measured relaxation
times of the plasmons, which suggests the importance of the electron-ion
coupling and s... | physics |
8,766 | Global minima of Al_N, Au_N and Pt_N, N=2-80, clusters described by Voter-Chen version of embedded-atom potentials | physics.atm-clus | Using the basin-hopping Monte Carlo minimization approach we report the
global minima for aluminium, gold and platinum metal clusters modelled by the
Voter-Chen version of the embedded-atom model potential containing up to 80
atoms. The virtue of the Voter-Chen potentials is that they are derived by
fitting to experime... | physics |
8,767 | A Density Functional Study of the Structure and Energetics of Small Hetero-Atomic Silicon-Carbon Nanoclusters | physics.atm-clus | The theoretical formalism of the local density approximation (LDA) to density
functional theory (DFT) has been used to study the electronic and geometric
structures of SimCn (1<=m, n<=4;n<=m) clusters. An all electron 6-311++G**
basis set has been used and complete geometry optimizations of different
possible structure... | physics |
8,768 | Calculation of van der Walls coefficients of alkali metal clusters by hydrodynamic approach to time-dependent density-functional theory | physics.atm-clus | In this paper we employ the hydrodynamic formulation of time-dependent
density functional theory to obtain the van der Waal coefficients $C_{6}$ and
$C_{8}$ of alkali-metal clusters of various sizes including very large
clusters. Such calculation becomes computationally very demanding in the
orbital-based Kohn-Sham for... | physics |
8,769 | Minimal mass-size of a stable 3He cluster | physics.atm-clus | The minimal number of 3He atoms required to form a bound cluster has been
estimated by means of a Diffusion Monte Carlo procedure within the fixed-node
approximation. Several importance sampling wave functions have been employed in
order to consider different shell-model configurations. The resulting upper
bound for th... | physics |
8,770 | Surface plasma resonance in small rare gas clusters by mixing IR and VUV laser pulses | physics.atm-clus | The ionization dynamics of a Xenon cluster with 40 atoms is analyzed under a
pum p probe scenario of laser pulses where an infrared laser pulse of 50 fs
length follows with a well defined time delay a VUV pulse of the same length
and peak intensity. The mechanism of resonant energy absorption due to the
coinc idence of... | physics |
8,771 | Cluster excitation and ionization in high velocity collisions:the atomic approach | physics.atm-clus | The independent atom and electron model [1] is introduced in a quantum
context and associated approximations tentatively estimated. Confrontation of
the model to measured ionization and excitation cross sections of small ionic
carbon clusters Cn+ in collisions with helium at an impact velocity of 2.6 a.u
is presented. | physics |
8,772 | Triatomic Molecular Systems and Three-body forces: The Ar_3 case | physics.atm-clus | We performed bound state calculations to obtain the first few vibrational
states for the Ar_3 molecular system. The equations used are of Faddeev-type
and are solved directly as three-dimensional equations in configuration space,
i.e. without resorting to an explicit partial wave decomposition. In addition
to realistic... | physics |
8,773 | $e^+ + H$ direct annihilation above the positronium formation threshold | physics.atm-clus | A long-standing problem with the solution of the Schr\"odinger equation has
been its inability to account for the electron-positron annihilation in
positron hydrogen scattering above the positronium formation threshold. This
letter shows that this problem has been resolved by the use of the modified
Faddeev equations. ... | physics |
8,774 | Modeling Na clusters in Ar matrices | physics.atm-clus | We present a microscopic model for Na clusters embedded in raregas matrices.
The valence electrons of the Na cluster are described by time-dependent
density-functional theory at the level of the local-density approximation
(LDA). Particular attention is paid to the semi-classical picture in terms of
Vlasov-LDA. The Na ... | physics |
8,775 | Geometrical and statistical factors in fission of small metal clusters | physics.atm-clus | Fission of metastable charged univalent metal clusters has been studied on
example of Na_{10}^{2+} and Na_{18}^{2+} clusters by means of density
functional theory methods. Energetics of the process, i.e. dissociation
energies and fission barriers, as well as its dynamics, i.e. fission pathways,
have been analyzed. The ... | physics |
8,776 | Stability of Small Neutral and Charged Strontium Clusters | physics.atm-clus | Dissociation and fission of small neutral, singly and doubly charged
strontium clusters are studied by means of ab initio density functional theory
methods and high-resolution time-of-flight mass spectrometry. Magic numbers for
small strontium clusters possessing enhanced stability towards monomer
evaporation and fissi... | physics |
8,777 | Large Magnetic Moments of Arsenic-Doped Mn Clusters and their Relevance to Mn-Doped III-V Semiconductor Ferromagnetism | physics.atm-clus | We report electronic and magnetic structure of arsenic-doped manganese
clusters from density-functional theory using generalized gradient
approximation for the exchange-correlation energy. We find that arsenic
stabilizes manganese clusters, though the ferromagnetic coupling between Mn
atoms are found only in Mn$_2$As a... | physics |
8,778 | On the crystal structure of lithium peroxide, Li2O2 | physics.atm-clus | The two published lithium peroxide structures, both ascribed to the hexagonal
P -6 space group, were subjected to reinterpretation and another more symmetric
structure, now belonging to the P 63/m m c space group, was found. Detailed
density-functional quantum mechanical calculations and crystal structure
optimisations... | physics |
8,779 | The planar-to-tubular structural transition in boron clusters from optical absorption | physics.atm-clus | The optical response of the lowest energy isomers of the B_20 family is
calculated using time-dependent density functional theory within a real-space,
real-time scheme. Significant differences are found among the absorption
spectra of the clusters studied. We show that these differences can be easily
related to changes... | physics |
8,780 | Study of coupled states for the (4s^{2})^{1}S + (4s4p)^{3}P asymptote of Ca_{2} | physics.atm-clus | The coupled states A^{1}\Sigma_{u}^{+} (^{1}D +}1}S), c^{3}\Pi_{u} (^{3}P +
^{1}S) and a^{3}\Sigma_{u}^{+} (^{3}P +}1}S) of the calcium dimer are
investigated in a laser induced fluorescence experiment combined with
high-resolution Fourier-transform spectroscopy. A global deperturbation
analysis of the observed levels,... | physics |
8,781 | Electron dynamics in strong laser pulse illumination | physics.atm-clus | We analyze the dynamics of up to $10^5$ electrons resulting from illuminating
a Xenon cluster with 9093 atoms with intense laser pulses of different length
and peak intensity. Interesting details of electron motion are identified which
can be probed with a time resolution of 100 attoseconds. Corresponding
experiments w... | physics |
8,782 | Optical absorption by magnesia-supported gold clusters and nanocatalysts: effects from the support, cluster and adsorbants | physics.atm-clus | Polarization-resolved optical spectra of magnesia-supported gold clusters
Au$_N$/MgO (N=1,2,4,8), bound at a surface color center $F_s$ of the MgO(100)
face, are calculated from the time-dependent density functional theory. The
optical lines for n=1,2 are dominated by transitions that involve strong
hybridization betwe... | physics |
8,783 | Laser-cluster interaction: x-ray production by short laser pulses | physics.atm-clus | We investigate the heating of the quasi-free electrons in large rare gas
clusters (N exceeding 10^5 atoms) by short laser pulses at moderate intensities
(I~10^{15} Wcm^{-2}). We identify elastic large-angle backscattering of
electrons at ionic cores in the presence of a laser field as an efficient
heating mechanism res... | physics |
8,784 | Numerical Study of Structural Phase Transitions in a Vertically Confined Plasma Crystal | physics.atm-clus | Dusty plasmas consists of an ionized gas containing small (usually negatively
charged) particles. Dusty plasmas are of interest in both astrophysics and
space physics as well as in research in plasma processing and nanofabrication.
In this work, the formation of plasma crystals confined in an external
one-dimensional p... | physics |
8,785 | Determination of the lowest energy structure of Ag$_8$ from first-principles calculations | physics.atm-clus | The ground-state electronic and structural properties, and the electronic
excitations of the lowest energy isomers of the Ag$_8$ cluster are calculated
using density functional theory (DFT) and time-dependent DFT (TDDFT) in real
time and real space scheme, respectively. The optical spectra provided by TDDFT
predict tha... | physics |
8,786 | Configuration interaction study of single and double dipole plasmon excitations in Na_8 | physics.atm-clus | We carry out a microscopic analysis of the ground and excited states of the
Na_8 metal cluster within the jellium model. We perform a series of
configuration interaction calculations on a Hartree-Fock basis and construct
eigenstates of the Hamiltonian which carry up to 4-particle 4-hole components.
Based on the analysi... | physics |
8,787 | Stability criterions of an oscillating tip-cantilever system in dynamic force microscopy | physics.atm-clus | This work is a theoretical investigation of the stability of the non-linear
behavior of an oscillating tip-cantilever system used in dynamic force
microscopy. Stability criterions are derived that may help to a better
understanding of the instabilities that may appear in the dynamic modes,
Tapping and NC-AFM, when the ... | physics |
8,788 | Stability of an oscillating tip in Non-Contact Atomic Force Microscopy: theoretical and numerical investigations | physics.atm-clus | This paper is a theoretical and a numerical investigation of the stability of
a tip-cantilever system used in Non-Contact Atomic Force Microscopy (NC-AFM)
when it oscillates close to a surface. No additional dissipative force is
considered. The theoretical approach is based on a variationnal method
exploiting a coarse ... | physics |
8,789 | Influence of noncontact dissipation in the tapping mode: Attempt to extract quantitative information on the surface properties with the local force probe method | physics.atm-clus | In the Tapping mode, a variation of the oscillation amplitude and phase as a
function of the tip sample distance is the necessary measurement to access
quantitatively to the properties of the surface. In the present work, we give a
systematic comparison between experimental data recorded on two surfaces, phase
and ampl... | physics |
8,790 | Nonlinear dynamical properties of an oscillating tip-cantilever system in the tapping mode | physics.atm-clus | The dynamical properties of an oscillating tip-cantilever system are now
widely used in the field of scanning force microscopy. The aim of the present
work is to get analytical expressions describing the nonlinear dynamical
properties of the oscillator in noncontact and intermittent contact situations
in the tapping mo... | physics |
8,791 | Growth kinetics of a nanoprotuberance under the action of an oscillating nanotip | physics.atm-clus | The atomic force microscope is a versatile tool that allows many routes to be
used for investigating the mechanical properties of soft materials on the
nanometer scale. In the present work, experiments were performed on polystyrene
polymer films of various molecular weight by approaching a vibrating nanotip
towards the... | physics |
8,792 | Nonlinear Dynamic Behavior of an Oscillating Tip-Microlever System and Contrast at the Atomic Scale | physics.atm-clus | In this paper the dynamic behavior of an oscillating tip-microlever system at
the proximity of a surface is discussed. We show that the nonlinear behavior of
the oscillator is able to explain the high sensitivity of the oscillating tip
microlever and the observed shifts of the resonance frequency as a function of
the t... | physics |
8,793 | Relationship between the non linear dynamic behaviour of an oscillating tip-microlever system and the contrast at the atomic scale | physics.atm-clus | In this paper, the dynamic behaviour of an oscillating tip-microlever system
at the proximity of a surface is discussed. The attractive tip-surface
interaction is simply described with a Van der Waals dispersive term and a
sphere-plane geometry. We show that the non linear behaviour of the oscillator
is able to explain... | physics |
8,794 | Stability analysis of an oscillating tip-cantilever system in NC-AFM | physics.atm-clus | This paper is a theoretical and a numerical investigation of the stability of
a tip-cantilever system used in noncontact atomic force microscopy (NC-AFM)
when it oscillates close to a surface. No additional dissipative force is
considered. The theoretical approach is based on a variational method
exploiting a coarse gr... | physics |
8,795 | Non-contact atomic force microscopy: Stability criterion and dynamical responses of the shift of frequency and damping signal | physics.atm-clus | The aim of this article is to provide a complete analysis of the behavior of
a noncontact atomic force microscope (NC-AFM). We start with a review of the
equations of motion of a tip interacting with a surface in which the stability
conditions are first revisited for tapping mode. Adding the equations of
automatic gain... | physics |
8,796 | Finite size effects in the dynamics and thermodynamics of 2D Coulomb clusters | physics.atm-clus | The dynamics and thermodynamics of melting in two-dimensional Coulomb
clusters is revisited using molecular dynamics and Monte Carlo simulations.
Several parameters are considered, including the Lindemann index, the largest
Lyapunov exponent and the diffusion constant. In addition to the orientational
and radial meltin... | physics |
8,797 | Cu-TBPP and PTCDA molecules on insulating surfaces studied by ultra-high-vacuum non-contact AFM | physics.atm-clus | The adsorption of two kinds of porphyrin (Cu-TBPP) and perylene (PTCDA)
derived organic molecules deposited on KBr and Al2O3 surfaces has been studied
by non-contact force microscopy in ultra-high vacuum, our goal being the
assembly of ordered molecular arrangements on insulating surfaces at room
temperature. On a Cu(1... | physics |
8,798 | Distance dependence of force and dissipation in non-contact atomic force microscopy on Cu(100) and Al(111) | physics.atm-clus | The dynamic characteristics of a tip oscillating in the nc-AFM mode in close
vicinity to a Cu(100)-surface are investigated by means of phase variation
experiments in the constant amplitude mode. The change of the quality factor
upon approaching the surface deduced from both frequency shift and excitation
versus phase ... | physics |
8,799 | Observation of individual molecules trapped on a nanostructured insulator | physics.atm-clus | For the first time, ordered polar molecules confined in monolayer-deep
rectangular pits produced on an alkali halide surface by electron irradiation
have been resolved at room temperature by non-contact atomic force microscopy.
Molecules self-assemble in a specific fashion inside pits of width smaller than
15 nm. By co... | physics |
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