Search results for "Interatomic potential"
showing 10 items of 19 documents
Casimir-Polder interatomic potential between two atoms at finite temperature and in the presence of boundary conditions
2007
We evaluate the Casimir-Polder potential between two atoms in the presence of an infinite perfectly conducting plate and at nonzero temperature. In order to calculate the potential, we use a method based on equal-time spatial correlations of the electric field, already used to evaluate the effect of boundary conditions on interatomic potentials. This method gives also a transparent physical picture of the role of a finite temperature and boundary conditions on the Casimir-Polder potential. We obtain an analytical expression of the potential both in the near and far zones, and consider several limiting cases of interest, according to the values of the parameters involved, such as atom-atom d…
Study of the different polymorphs of alumina and transitional phases appearing in the first oxidation stage of aluminium : simulation at the atomic s…
2014
The goal of this work is to develop a new SMTB-Q potential in order to study the early stages of the oxidation of aluminium by molecular dynamics (MD).Our potential is able to model different alumina polymorphs as well as transitions from the amorphous state to a crystalline phase. Our approach couples a covalent term with the charge. It uses Rapp_ and Goddard scheme for the electrostatic part and the model of alternating network developed by C. Noguera for the covalent part.The SMTB-Q potential was validated with a Monte Carlo approach. This study shows that the potential SMTB-Q gives satisfactory results for the Al-O bonding in different atomic configurations. The bonding results from the…
Semiquantum molecular dynamics simulation of thermal properties and heat transport in low-dimensional nanostructures
2012
We present a detailed description of the semi-quantum approach to the molecular dynamics simulation of stochastic dynamics of a system of interacting particles. Within this approach, the dynamics of the system is described with the use of classical Newtonian equations of motion in which the quantum effects are introduced through random Langevin-like forces with a specific power spectral density (the color noise). The color noise describes the interaction of the molecular system with the thermostat. We apply this technique to the simulation of the thermal properties of different low-dimensional nanostructures. Within this approach, we simulate the specific heat and heat transport in carbon n…
On the Ground State Structure of Adsorbed Monolayers: Can One Find them by Monte Carlo Simulation?
2002
While the classical ground state structure of an atomic monolayer adsorbed at a noncorrugated perfectly flat substrate trivially is a triangular lattice, the spacing being the minimum of the interatomic potential, nontrivial structures occur on corrugated substrates. This problem is exemplified for the (100) face of a face-centered cubic crystal, varying both the density of the adsorbed monolayer and the strength of the potential due to the surface. Increasing the density beyond that of the commensurate c(2 x 2) structure, incommensurate patterns become stable with “heavy” walls (HW) oriented along the face diagonals [including the “crossing heavy walls” (CRHW) phase]. It is shown that slow…
Casimir-Polder forces, boundary conditions and fluctuations
2008
We review different aspects of the atom-atom and atom-wall Casimir-Polder forces. We first discuss the role of a boundary condition on the interatomic Casimir-Polder potential between two ground-state atoms, and give a physically transparent interpretation of the results in terms of vacuum fluctuations and image atomic dipoles. We then discuss the known atom-wall Casimir-Polder force for ground- and excited-state atoms, using a different method which is also suited for extension to time-dependent situations. Finally, we consider the fluctuation of the Casimir-Polder force between a ground-state atom and a conducting wall, and discuss possible observation of this force fluctuation.
Modelling of the cation motions in complex system: case of Na-mordenites
2002
Abstract Semi-empirical inter-atomic potentials and Monte Carlo algorithms are proposed to predict the evolution of the interaction energy between sodium ions and a mordenite type aluminosilicate network as a function of Si/Al ratio. This result is favourably compared with the activation energy barriers for Na + `jumps' responsible for the polarization change, measured by thermally stimulated current (TSC) spectroscopy, for Na-mordenites characterized by Si/Al ratios ranged from 5.5 to 12. Finally, we propose a possible mechanism for the cation motions, which involves activation barriers within the same order of magnitude than those measured by TSC.
Prediction of structural and thermodynamic properties of zinc-blende AlN: molecular dynamics simulation
2004
Abstract Structural and elastic properties of AlN are investigated by using a molecular dynamics simulation based on the Tersoff empirical interatomic potential. Both of zinc-blende and rock-salt structures are discussed. The calculated bulk properties and elastic constants agree well with the available experimental and theoretical data. The Thermodynamic properties in zinc-blende structure are also predicted including the Debye temperature, melting temperature, heat capacity, linear thermal coefficient. This study is helpful to understand the bahviour of physical properties of AlN when the temperature varies.
High-Pressure, High-Temperature Phase Diagram of Calcium Fluoride from Classical Atomistic Simulations
2013
We study the phase diagram of calcium fluoride (CaF2) under pressure using classical molecular dynamics simulations performed with a reliable pairwise interatomic potential of the Born−Mayer−Huggins form. Our results obtained under conditions 0 ≤ P ≲ 20 GPa and 0 ≤ T ≲ 4000 K reveal a rich variety of multiphase boundaries involving different crystal, superionic, and liquid phases, for all of which we provide an accurate parametrization. Interestingly, we predict the existence of three special triple points (i.e., solid−solid−superionic, solid−superionic−superionic, and superionic−superionic−liquid coexisting states) within a narrow and experimentally accessible thermodynamic range of 6 ≤ P …
A tight-binding potential for the simulation of solid and liquid iodine
2003
In this work, we suggest an interatomic potential for iodine applicable to the simulation of the condensed phases of the halogen within the temperature and density range accessible to experiments. The potential includes an attractive term that is partitioned into directional chemical bonding with a many-particle character and a pairwise interaction. Despite its simplicity, the potential reproduces the crystal structure of solid iodine, the presence of atomic phases with increasing pressure, and the metallic or insulating character of the solid phases. Finally, we present preliminary simulation results for fluid iodine.
Structure of Liquids
2014
An Introduction to the description of the static structure of simple liquids is given. The principle quantity, which describes this structure is the structure factor, which can be measured with neutron and X-ray diffraction. The structure factor is the Fourier transform of the radial pair distribution function, which describes the statistics of the atoms around a given one. Several theories are introduced for calculating this quantities. It is shown that the structure of liquid metals is dominated by their hardcore repulsion. In the low-wavenumber limit the structure factor is related to the compressibility of the liquid. In this limit deviations from the hard-core model become importent, w…