Chain structure and electronic states of liquid Rb-Se mixtures byab initiomolecular-dynamics simulations

The effects of excess electronic charges transferred from alkali metals to Se atoms on the chain structure in liquid Rb_xSe_<1−x> for x≤0.5 are investigated by means of ab initio molecular-dynamics simulations. It is found that the interaction between Se chains is enhanced by the transferred electrons, and that the average length of Se chains becomes shorter with increasing alkali-metal concentration. The shortening of Se chains is responsible for an increase of electronic states at the Fermi level, which explains the observed increase of the electrical conductivity on the addition of alkali metals. At the equiatomic concentration, there are almost no electronic states at the Fermi level due to the formation of Se^<2−>_2 dimers. The alkali-metal-concentration dependence of the bonding properties between Se atoms is discussed in comparison with liquid alkali-metal tellurides based on a population analysis