Phase transition and electronic properties of Co-As binary compounds at high pressure.

Abstract

New stable stoichiometries in the Co–As system are investigated up to 100 GPa by the CALYPSO structure prediction method. In particular, we found three novel stable compounds of Co2As-Pnma, CoAs2-Pnnm, and CoAs3-C2/m at high pressure. According to the theoretical electronic band structures, the structures of Co2As-Pnma, CoAs2-Pnnm, and CoAs3-C2/m have metallic characters, and a pressure-induced electronic topological transition was found in CoAs3-C2/m, which is not shown in other stoichiometries of the Co–As system. The calculated results of the electron localization function show that there are polar covalent bond interactions between Co atoms and As atoms in CoAs2-Pnnm and CoAs3-C2/m. The present results can be helpful for understanding diverse structures and properties of Co–As binary compounds under high pressure.