Structural, mechanical and electronic properties of CaB₂C₂ at high pressure

College of Physics and Optoelectronic Technology, Nonlinear Research Institute, Baoji University of Arts and Sciences - Baoji 721016, China

^(a) scu_zheng@163.com

Received: 23 July 2017
Accepted: 4 August 2017

Abstract

Under high pressure, the graphite-like materials present complex structural behaviors, interesting mechanical properties, and fascinating electronic structures. We here report two novel high-pressure structures of oF40-CaB₂C₂ and HPtI20-CaB₂C₂ by using the newly developed particle swarm optimization algorithm based on first-principles calculations. The oF40-CaB₂C₂ and HPtI20-CaB₂C₂ exhibit a 3D sp³ B-C bonded network under compression, which is verified by the inspections of their crystal structures and partial densities of states. The study of mechanical anisotropy reveals that the degree of anisotropy for CaB₂C₂ is gradually enhanced with its structural transformations under pressure. Intriguingly, the originally indirect band-gap CaB₂C₂ at ambient pressure transform into a direct band-gap semiconductor under extreme pressure (beyond 214.4 GPa).