Concentration Dependence of the Dynamic Properties of Liquid TlxSe1-x Based on Ab initio Molecular-Dynamics Simulations

The concentration dependence of the dynamic properties of liquid TlxSe1-x alloys is investigated by ab initio molecular-dynamics simulations. In the concentration range x = 0.0 to 0.67, the highest diffusivity occurs at approximately x = 0.2 with the existence of fairly long Se chains in the liquid. Upon the further addition of Tl atoms, the self-diffusion coefficients of both Se and Tl decrease despite the shortening of the Se chain length. This behavior is due to the suppression of self-diffusion by the increase in the strength of electrostatic interactions between Tl and Se atoms. The concentration dependence of the ionic conductivity is discussed on the basis of the fluctuation-dissipation theorem as well as the Nernst-Einstein relation.