Phase transition of CaTe induced by high-pressure: Structural and elastic DFT study of five structures

Abstract

In this work, a detailed study of the structural and mechanical properties of crystalline CaTe with five different forms in pressure range of 0–60 GPa is performed by density-functional theory (DFT) calculations. The obtained structural parameters are in good agreement with experimental and other theoretical data at 0 GPa. Then, the analysis of the variation tendencies of enthalpy difference with increasing pressure among these five phases show that CaTe is NaCl-type (B1) structure at 0 GPa, and transforms to an intermediate structure of P4/nmm at 27.8–28.1 GPa, then transforms to CsCl-type (B2) structure at 32.9–36.9 GPa. The quite small enthalpy difference between P4/nmm and B2 structure indicate the possibility of coexistence of these two phase at high pressures. Besides, between 27 and 28 GPa, the enthalpy difference among four structures (NaCl, CsCl, P4/nmm, MnP) is quite close, and there is the possibility of more structural coexistence at this range of pressure. Furthermore, we study the pressure dependence of mechanical properties of CaTe, and the change of the elastic constants. The major elastic moduli with pressure are also described, and the calculated stability conditions indicating the intermediate structure is possibly unstable.