DENSITY-FUNCTIONAL CALCULATIONS FOR ZINTL SYSTEMS - STRUCTURE, ELECTRONIC-STRUCTURE AND ELECTRICAL-CONDUCTIVITY OF LIQUID NASN ALLOYS

Molecular dynamics (MD) simulations are presented for five different c ompositions of liquid NaSn alloys, covering the range from 20 to 80% s odium. We apply an nb initio (Car-Parrinello) method as well as an app roximate LCAO-DFT scheme. The two methods yield similar results: the t in atoms form large dynamic networks. Only for the sodium-rich composi tion are isolated tin atoms and dimers observed. From the ab initio MD trajectories the structure factors, the total and partial densities o f 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 compos ition and show good agreement with experimental data. We give a detail ed 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 acc ord with experimental data.