材料期刊网

The thermal-expansion behaviors of zincblende GaP, GaAs, GaSb, BP, BAs, and BSb are comparatively studied by first-principles response-function calculation. In contrast to these gallium phases and the most of other III-V semi conductors, low-temperature negative thermal expansion is not found in the three borides. In order to explore the reason for the difference, the roles of the pressure-induced redistributions of the static and dynamic charges in the lattice-dynamic process of these phases are analyzed in details. Our Study shows that the static charge moves towards the bond center and the dynamic effective charge decreases as a hydrostatic pressure is applied to these gallium phases, which leads to the reductions in their polarity and ionicity. However, both of the static and dynamic charges behave inversely in the three borides. As a result, these borides' polarity and ionicity will increase under pressure. The fact suggests a correlation between polarity reduction and negative thermal expansion in III-V semiconductors.