A larger-cell tetragonal carbon allotrope tP176 carbon with superhardness

Abstract

• A new larger carbon allotrope t P176 carbon with P 4/ nbm phase is first proposed. • The t P176 carbon is a potentially superhard material with hardness of 55 GPa. • t P176 carbon is a wide and quasi-direct band gap semiconductor material. A new allotrope of sp 3 hybrid superhard carbon, t P176 carbon, is proposed and investigated in this work. The t P176 carbon is dynamically, thermodynamically and mechanically stable, respectively. The bulk modulus ( B ) and shear modulus ( G ) of t P176 carbon are 242 GPa, and 192 GPa, respectively. In addition, t P176 carbon is a wide band gap semiconductor material with quasi-direct band gap, and the band gap is 2.892 eV. The hardness of t P176 carbon is 55 GPa, which implies that it is a potentially superhard material.