Poly-Anions in Liquid CsPb: An ab initio Molecular-Dynamics Simulation

Most alkali-group-IV liquid alloys exhibit strong chemical effects leading to well-defined equiatomic compounds. This is generally explained by the survival of particular clusters of lead-''Zintl'' ions-in the liquid state. We report on an ab initio simulation of liquid CsPb, for which the chemical ordering is believed to be particularly strong. Good agreement with experiment is obtained, provided the valence states of cesium include the 5s and 5p states. The liquid contains a much richer variety of Pb conformations than isolated Pb4 units only. This is in accordance with the expectation that with increasing temperature the isolated ''Zintl'' ions break down rapidly.