M. Silbert

Liquid metals with structure factor shoulders

Abstract Some liquid metals (e.g. Ga, Sn, Sb, Bi) exhibit a low lying shoulder on the high angle side of the principal peak in the structure factor. This feature is compatible with an interatomic potential consisting essentially of a hard core together with an adjacent ledge. Such a potential is entirely consistent with electron theory.

Static structure and ionic transport in molten AgBr and AgCl

The static structure of molten AgBr and AgCl have been calculated using the hypernetted chain theory of liquids (HNC) and molecular dynamics simulations (MD) with effective potentials based on the functional form originally proposed by Vashishta and Rahman [Phys. Rev. Lett. 40, 1337 (1978)] to study α-AgI. The HNC and MD are in good agreement among themselves as well as in good qualitative agreement with experiment. MD simulations have been also used to calculate the time correlation functions and ionic transport properties of these melts. The results for the velocity autocorrelation functions suggest, in both cases, a mechanism for diffusion akin to that we suggested for molten AgI and CuX (X=Cl, Br, I) [J. Phys. Condens. Matter 2, 6643 (1990)] even though the cations velocity autocorrelation function is no longer purely diffusive. The results for the diffusion coefficients resemble the type of behavior found in superionic melts, as if the transition to a superionic state is finally realized in AgCl and ...

Interionic Interactions in Transition Metals. Application to Vanadium

Abstract A new model is proposed for transition metals to obtain effective interionic pair potentials. The local form factor combines the empty-core model, which accounts for the nearly free electron band, and a contribution giving all the features associated with the d band obtained by an inverse scattering approach. The effective interionic pair potentials depends on two parameters. The first is the core radius; the second is a measure of the softness of the repulsive potential. The influence of the parametrisation on the pair potential for vanadium is studied, and the results are compared with other potentials available in the literature.

A theoretical study of the static structure and thermodynamics of liquid lithium

The authors have studied the static structure and some thermodynamic properties of liquid lithium by using the variational modified hypernetted chain (VMHNC) approximation as the liquid state theory and several effective interatomic pair potentials, derived from different pseudopotentials already proposed in the literature. They also propose a new interatomic pair potential derived from the neutral pseudoatom method (NPA).

Structure and thermodynamics of hard D-dimensional spheres : overlap volume function approach

A very simple ansatz for the direct correlation functions of hard D-dimensional spheres is presented. For D = 1 and 3, it reduces exactly to the Percus-Yevick (PY) theory, yielding results which are very close to the PY theory for the other dimensions. A generalized Carnahan-Starling equation of state is proposed, which is in excellent agreement with the available computer simulation results. Finally, a generalized Verlet-Weis procedure for the pair distribution function g(r, η), is proposed. The important case of hard discs (D = 2) is studied in detail, leading to excellent results for g(r, η).

Variational MHNC calculations of the structure of expanded liquid rubidium

Abstract The structure factor, S(q), of liquid rubidium has been calculated for several states along the saturated vapour-pressure curve ranging from the melting point up to the critical point. The calculations are based on the variational modified hypernetted chain approximation (VMHNC) and an effective pair potential derived from pseudopotential perturbation theory. Good agreement with the experimental S(q) is found for temperatures up to 1600 K.

A quantum field theory of phonons in two-component liquids with large mass difference

Abstract A quantum field theory of the structure of phonons in multi-component liquids is applied to the case of a binary mixture with large mass difference between their components. We show that the coupling between light atoms dominates all other couplings. In the short-wavelength regime collective modes appear that resemble fast and slow sound.

Liquid structure of the 3d transition metals

The results of calculations of the static structure factors, S(q), for liquid 3d transition metals are presented. These have been studied using effective interionic pair potentials derived from a local approach that combines the empty-core model to describe the nearly free electron sp band with a d-band contribution deduced from an inverse scattering method. The liquid structure is calculated using the variational hypernetted chain theory. The resulting S(q)s agree reasonably well with the experimental X-ray diffraction data.

Theory of phase equilibria in polymer stabilized colloidal suspensions

The results of calculations describing the observed phase behaviour of polymer stabilized colloidal dispersions based on the Gibbs-Bogolyubov variational approach are presented. The effective pairwise additive macroparticle interaction is assumed to be a superposition of Yukawa potentials. Hardspheres are chosen as the reference system for the disordered phases, while an Einstein model is taken to be a suitable reference system for the ordered phases. In sterically stabilized colloidal dispersions, temperature variations in the range of the repulsive steric interaction between macroparticles are allowed. Additional insight into the temperature dependence of the adsorbed polymer layer thickness is obtained by comparing the results of the variational approach with those obtained using the phenomenological Flory-Huggins theory of phase separation. In order to describe the observed reversible depletion flocculation, the double Yukawa model potential permits changes in the depletion attraction with free polyme...

A polarizable ion model for the structure of molten CuI

The results are reported of the molecular dynamics simulations of the coherent static structure factor of molten CuI at 938 K using a polarizable ion model. This model is based on a rigid ion potential to which the many body interactions due to the anions induced polarization are added. The calculated structure factor reproduces the clear sharp prepeak observed in neutron diffraction data. The corresponding partial structure factors and the related radial distribution functions calculated by molecular dynamics are compared with those found in the literature derived from a combination of neutron and x-ray diffraction data with the aid of the reverse Monte Carlo simulation technique, as well as those calculated by ab initio MD simulations.The results are reported of the molecular dynamics simulations of the coherent static structure factor of molten CuI at 938 K using a polarizable ion model. This model is based on a rigid ion potential to which the many body interactions due to the anions induced polarization are added. The calculated structure factor reproduces the clear sharp prepeak observed in neutron diffraction data. The corresponding partial structure factors and the related radial distribution functions calculated by molecular dynamics are compared with those found in the literature derived from a combination of neutron and x-ray diffraction data with the aid of the reverse Monte Carlo simulation technique, as well as those calculated by ab initio MD simulations.