Novel boron nitride polymorphs with graphite-diamond hybrid structure

TL;DR

This paper proposes five new boron nitride polymorphs with hybrid graphite-diamond structures, revealing their exceptional mechanical and electronic properties and explaining previously unexplained diffraction patterns.

Contribution

Theoretical prediction of five novel BN polymorphs with hybrid structures, expanding understanding of phase transitions and properties of boron nitride materials.

Findings

Possess high hardness and ductility

Exhibit diverse electronic behaviors including semi-conductivity and semi-metallicity

Explain previously unresolved diffraction patterns

Abstract

Both boron nitride (BN) and carbon (C) have sp, sp2 and sp3 hybridization modes, and thus resulting in a variety of BN and C polymorphs with similar structures, such as hexagonal BN (hBN) and graphite, cubic BN (cBN) and diamond. Here, five types of BN polymorph structures were proposed theoretically, inspired by the graphite-diamond hybrid structures discovered in recent experiment. These BN polymorphs with graphite-diamond hybrid structures possessed excellent mechanical properties with combined high hardness and high ductility, and also exhibited various electronic properties such as semi-conductivity, semi-metallicity, and even one- and two-dimensional conductivity, differing from known insulators hBN and cBN. The simulated diffraction patterns of these BN hybrid structures could account for the unsolved diffraction patterns of intermediate products composed of "compressed hBN" and diamond-like BN, caused by phase transitions in previous experiments. Thus, this work provides a theoretical basis for the presence of these types of hybrid materials during phase transitions between graphite-like and diamond-like BN polymorphs.