Molecular dynamics (MD) simulations are presented for five different compositions of liquid NaSn alloys, covering the range from 20 to 80% sodium. We apply an ab initio (Car-Parrinello) method as well as an approximate LCAO-DFT scheme. The two methods yield similar results: the tin atoms form large dynamic networks. Only for the sodium-rich composition are isolated tin atoms and dimers observed.From the ab initio MD trajectories the structure factors, the total and partial densities of states, the charge distributions and, by means of the Kubo-Greenwood formula, the electrical conductivities are calculated. The structure factors and the conductivities are obtained as functions of the composition and show good agreement with experimental data.We give a detailed discussion of the concentration dependence of the structure factors, the total and partial densities of states, the charge distributions and the electrical conductivities. The behaviour and the origin of the prepeak is discussed. For the equimolar composition the dependence of the conductivity on temperature is obtained and is in qualitative accord with experimental data.
Liquid NaSn alloys in five different compositions (20, 40, 50, 57 and 80% sodium) are studied using density functional calculations combined with molecular dynamics (Car-Parrinello method). The frequency-dependent electric conductivities for the systems are calculated by means of the Kubo-Greenwood formula.The extrapolated DC conductivities are in good agreement with the experimental data and reproduce the strong variation with the concentration. The maximum of conductivity is obtained, in agreement with experiment, near the equimolar composition.The strong variation of conductivity, ranging from almost semiconducting up to metallic behaviour, can be understood by an analysis of the densities-of-states.
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