D. J. González

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).

Orbital free ab initio molecular dynamics study of liquid Al near melting

The orbital free ab initio molecular dynamics method is applied to study the static and dynamic structure of liquid Al near the triple point. The method uses a new kinetic energy functional, along with a local pseudopotential constructed within the same kinetic energy functional. The results obtained for the dynamic structure factor are compared with recent experimental data.

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).

Structural and dynamical properties of liquid Mg. An orbital-free molecular dynamics study

Several static and dynamic properties of liquid magnesium near melting have been evaluated by the orbital-free ab initio molecular dynamics method. The calculated static structure shows good agreement with recent experimental data, including an asymmetric second peak in the structure factor which has been linked to the existence of an important icosahedral short-range order in the liquid. As for the dynamic structure, we obtain collective density excitations with an associated dispersion relation which closely follows recent experimental results. Accurate estimates have also been obtained for several transport coefficients.

Ab initio molecular dynamics study of the static, dynamic, and electronic properties of liquid mercury at room temperature

We report a study on several static, dynamic, and electronic properties of liquid Hg at room temperature. We have performed ab initio molecular dynamics simulations using Kohn-Sham density functional theory combined with a nonlocal ultrasoft pseudopotential. The calculated static structure shows good agreement with the available experimental data. We present results for the single-particle dynamics, and recent experimental data are analyzed. The calculated dynamic structure factors S(q,omega) fairly agree with their experimental counterparts as measured by inelastic x-ray (and neutron) scattering experiments. The dispersion relation exhibits a positive dispersion, which however is not so marked as suggested by the experiment; moreover, its slope at the long-wavelength limit provides a good estimate of the experimental sound velocity. We have also analyzed the dynamical processes behind the S(q,omega) in terms of a model including a relaxation mechanism with both fast and slow characteristic time scales.

DYNAMICAL PROPERTIES OF LIQUID LITHIUM ABOVE THE MELTING POINT

The dynamical properties of liquid lithium at several thermodynamic states near the triple point have been studied within the framework of the mode-coupling theory. We present a self-consistent scheme which, starting from the knowledge of the static structural properties of the liquid system, allows the theoretical calculation of several single particle and collective dynamical properties. The study is complemented by performing molecular-dynamics simulations and the obtained results are compared with the available experimental data.

Density fluctuations and single-particle dynamics in liquid lithium

The single-particle and collective dynamical properties of liquid lithium have been evaluated at several thermodynamic states near the triple point. This is performed within the framework of mode-coupling theory, using a self-consistent scheme which, starting from the known static structure of the liquid, allows the theoretical calculation of several dynamical properties. Special attention is devoted to several aspects of the single-particle dynamics, which are discussed as a function of the thermodynamic state. The results are compared with those of Molecular Dynamics simulations and other theoretical approaches.

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.

Surface structure in simple liquid metals. An orbital free first principles study.

Molecular dynamics simulations of the liquid-vapor interfaces in simple sp-bonded liquid metals have been performed using first-principles methods. Results are presented for liquid Li, Na, K, Rb, Cs, Mg, Ba, Al, Tl, and Si at thermodynamic conditions near their respective triple points, for samples of 2000 particles in a slab geometry. The longitudinal ionic density profiles exhibit a pronounced stratification extending several atomic diameters into the bulk, which is a feature already experimentally observed in liquid K, Ga, In, Sn, and Hg. The wavelength of the ionic oscillations shows a good scaling with the radii of the associated Wigner-Seitz spheres. The structural rearrangements at the interface are analyzed in terms of the transverse pair correlation function, the coordination number, and the bond-angle distribution between nearest neighbors. The valence electronic density profile also shows (weaker) oscillations whose phase, with respect to those of the ionic profile, changes from opposite phase in the alkalis to almost in-phase for Si.

Pseudopotentials for the calculation of dynamic properties of liquids

The calculation of dynamic properties of physical systems requires the knowledge of their total energy as a function of their configuration. In this paper we review some techniques for making this evaluation feasible in liquid systems, in particular liquid metals, through the use of pseudopotentials, and we also discuss how to construct the pseudopotentials in order to optimize their use within approximate theories for the total energy. Some results are given for pure metals and alloys.