A novel superhard phase of TiB3 predicted by first-principles calculation

Abstract

A novel superhard structure of TiB3 is predicted and its phase transitions, mechanical properties and electronic structure up to 200 GPa are studied employing first-principles calculation. We propose a new structure by substituting the highly stable Amm2 structure with excellent mechanical properties in VB3. Enthalpy calculations demonstrate its superior energetic stability compared to the previously predicted C2/m structure via particle swarm optimization. Furthermore, it maintains stability up to 93.8 GPa and transforms into a P2/m structure under further compression. The Amm2 structure stands as a novel superhard phase with a hardness of 51.6 GPa by Chen’s model, surpassing the C2/m structure by 3.2 GPa. This disparity arises from structural distinctions, with the Amm2 structure featuring boron plates consisting of more layers, resulting in stronger B-B interactions. This novel superhard structure stands as the hardest reported Ti-B compound to date, poised to replace conventional superhard material c-BN in cutting tools and wear-resistant coatings.

Keywords

• TiB3
• Structure prediction
• Phase transition
• Mechanical properties
• High pressure