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Classical molecular dynamics simulations are performed on LiF in the framework of the polarizable ion model. The overlap repulsion and polarization terms of the interaction potential are derived on a purely non-empirical, first-principles basis. For the dispersion, three cases are considered: a first one in which the dispersion parameters are set to zero and two others in which they are included, with different parametrizations. Various thermodynamic, structural and dynamic properties are calculated for the solid and liquid phases. The melting temperature is also obtained from direct coexistence simulations of the liquid and solid phases. Dispersion interactions appear to have an important effect on the densities of both phases and on the melting point, although the liquid properties are not affected when simulations are performed in the NVT ensemble at the experimental density.

The relationships between the ionic mobility, the viscosity, and the atomic-scale structure are investigated in computer simulations of mixtures of LiF and the network glass-forming material BeF(2). The simulations span a wide range of compositions, across which the fluidity of the system changes greatly due to the break-up of the Be-F network by the addition of the LiF. The relationship between the conductivity and viscosity passes from that expected for independently diffusing ions in the dilute mixtures to strongly decoupled Li+ migration through a viscous network at higher concentrations. The transition between these régimes is linked to the changing local and intermediate-scale structure in the melts. The decoupling phenomenon is associated with the appearance of migration channels in the network which leads to cooperative effects in the Li+ migration.

Abstract: In this study, we present new experimental heat capacity data of solid and liquid phase of CsF covering the temperature range from 5K to 1400K. The low temperature data were obtained by adiabatic calorimetry and compared with the theoretical heat capacity computed from ab initio harmonic crystal approximation. The absolute entropy at T =298.15K determined based on the presented results is . The high temperature heat capacity was measured using a drop calorimeter and the data for the solid phase revealed significant excess properties. The data for the liquid phase were correlated with the molecular dynamic simulation obtaining a good agreement. The recommended molar heat capacity of the CsF solid phase is:and the one of the liquid phase was determined as:From the calorimetric results the enthalpy of fusion of CsF was determined as: [Copyright &y& Elsevier]