[en] It is shown that a discretized version of Feynman's path integral provides a convenient tool for the numerical investigation of the properties of an electron solvated in molten KCl. The binding energy and the pair correlation functions are calculated. The local structure around the solute electron appears to be different from that of an F center in the solid

[en] With use of a Lagrangian which allows for the variation of the shape and size of the periodically repeating molecular-dynamics cell, it is shown that different pair potentials lead to different crystal structures

[en] It is shown that the elastic strain fluctuations are a direct measure of elastic compliances in a general anisotropic medium; depending on the ensemble in which the fluctuation is measured either the isothermal or the adiabatic compliances are obtained. These fluctuations can now be calculated in a constant enthalpy and pressure, and hence, constant entropy, ensemble due to recent develpments in the molecular dynamics techniques. A calculation for a Ni single crystal under uniform uniaxial 100 tensile or compressive load is presented as an illustration of the relationships derived between various strain fluctuations and the elastic modulii. The Born stability criteria and the behavior of strain fluctuations are shown to be related

[en] A new Lagrangian formulation is introduced. It can be used to make molecular dynamics (MD) calculations on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamical equations given by this Lagrangian. This new MD technique is well suited to the study of structural transformations in solids under external stress and at finite temperature. As an example of the use of this technique we show how a single crystal of Ni behaves under uniform uniaxial compressive and tensile loads. This work confirms some of the results of static (i.e., zero temperature) calculations reported in the literature. We also show that some results regarding the stress-strain relation obtained by static calculations are invalid at finite temperature. We find that, under compressive loading, our model of Ni shows a bifurcation in its stress-strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. It is suggested that such a transformation could perhaps be observed experimentally under extreme conditions of shock

[en] This paper deals with a classical fluid of positive and negative ions at liquid-state densities; tipically, a molten alkalihalide. It is mostly concerned with recent advances in microscopic understanding associated with correlations between charge density fluctuations and their interplay with mass density fluctuations and with single-ion motion. A brief review of related areas which hold promise of future development is also presented

[en] The analytic approximation applied by Gillan to a classical one-component plasma, in which short-range correlations are grafted onto a Debye-Hueckel theory through a hard-sphere boundary condition on the pair correlation function, is examined in a two-component plasma over wide ranges of temperature, densities, and valences. The results for the thermodynamics and the structure of these systems are in good agreement with available Monte Carlo data and generally very close to those yielded by the hypernetted-chain approximation. (author)

[en] The αarrow-right-leftß phase transition in AgI is studied with use of the new molecular-dynamics technique which allows for a dynamical variation of the shape and size of the cell. In the present model, upon heating of ß-AgI, the iodine ions undergo a hcp→bcc transformation and silver ions become mobile, whereas the reverse transformation is observed on cooling of α-AgI. The calculated αarrow-right-leftß transition temperature and structural and dynamical properties are in good agreement with experiments

[en] The F-centre model for the bound state and the first optical transition of an electron in a metal-molten salt solution is examined in the high dilution limit appropriate for comparison with optical absorption data. It is first argued that the model is consistent with recent neutron diffraction and computer simulation data on the structure of pure molten salts, and not incompatible with an Anderson localization model for the electronic conductivity of the solution at higher concentration of metal. A detailed evaluation of the model is presented for the case of a molten salt of equi-sized ions simulating molten KCl. The treatment of the electronic states is patterned after semicontinuum approximations previously applied to the F-centre in ionic crystals, but the equilibrium radius of the electronic cavity and its fluctuations are determined self-consistently from the free energy of the solution. The detailed analysis of this case and the agreement of the results with experiment allow the construction of a simple parametrization scheme, which is then applied to explore the trends of the optical absorption spectrum and of the volume of mixing through the whole family of M-MX solutions, where M is an alkali and X a halogen. Similarities and differences of the electronic bound state in the crystal and in the liquid are underlined. (author)

No abstract available

[en] A short review is given of the main structural and dynamical properties of molten alkali halides. Particular emphasis is put on their collective dynamical properties and the present experimental evidence for optic modes in these fluids is examined. It is concluded that these modes do exist at long wavelengths in LiF. (author)