A novel superhard boron nitride polymorph with monoclinic symmetry

Abstract

In this work, a new superhard material named Pm BN is proposed. The structural properties, stability, mechanical properties, mechanical anisotropy properties, and electronic properties of Pm BN are studied in this work. Pm BN is dynamically and mechanically stable, the relative enthalpy of Pm BN is greater than that of c-BN, and in this respect, and it is more favorable than that of T-B3N3, T-B7N7, tP24 BN, Imm2 BN, NiAs BN, and rocksalt BN. The Young’s modulus, bulk modulus, and shear modulus of Pm BN are 327 GPa, 331 GPa, and 738 GPa, respectively, and according to Chen’s model, Pm BN is a novel superhard material. Compared with its original structure, the mechanical anisotropy of Young's modulus of Pm BN is larger than that of C14 carbon. Finally, the calculations of the electronic energy band structure show that Pm BN is a semiconductor material with not only a wide band gap but also an indirect band gap.

BN Polymorphs in Hexagonal 2–7 Stacking Orders: First-Principles and High-Throughput Study

“…In particular, many important achievements have been made in the exploration of superhard materials and electronic materials for light elements. − As a new generation of semiconductor materials, 3C BN can not only be used to fabricate electronic devices under extreme conditions such as high temperature, high frequency, and high power but also have wide application prospects in deep ultraviolet luminescence and detectors. Boron nitride materials may exhibit excellent properties of superhardness, − ductility, − , an ultrawide bandgap, − or, more rarely, the electronic property of metallicity. − …”