Polyanionic and octet phases in the K-Sb system. II. Liquid alloys

Abstract

The structural, dynamic, and electronic properties of liquid ${\mathrm{K}}_{3}$Sb and KSb alloys have been investigated using ab initio density-functional molecular dynamics. We demonstrate that as for the corresponding crystalline compounds the chemical bonding is determined by a generalized Zintl principle. Consequently, the local order in the liquid is similar to that in the crystalline phases: in the octet composition the dominant feature is Coulombic charge ordering. In the covalent equiatomic composition the Sb atoms share valence electrons in polyanionic clusters forming short, entangled Sb chains. The $\mathrm{pp}\ensuremath{\sigma}$ bonds stabilizing the clusters in the liquid and the helical ${\mathrm{Sb}}_{\ensuremath{\infty}}$ chains in crystalline KSb possess considerable flexibility. Therefore, the electronic structure of crystalline and liquid alloys (and consequently their physicochemical properties) are very similar, although the local order is considerably blurred in the melt.