Crystal Structures of CaB3N3 at High Pressures

Abstract

Using global structure searches, we have explored the structural stability of CaB$_3$N$_3$, a compound analogous to CaC$_6$, under pressure. There are two high-pressure phases with space groups $\textit{R3c}$ and $\textit{Amm2}$ that were found to be stable between 29 and 42 GPa, and above 42 GPa, respectively. The two phases show different structural frameworks, analogous to graphitic CaC$_6$. Phonon calculations confirm that both structures are also dynamically stable at high pressures. The electronic structure calculations show that the $\textit{R3c}$ phase is a semiconductor with a band gap of 2.21 eV and that the $\textit{Amm2}$ phase is a semimetal. These findings help advance our understanding of the Ca-B-N ternary system.