Two novel large-cell boron nitride polymorphs

Abstract

Based on density functional theory, two novel sp2-hybridized cubic boron nitride (cP128 BN and cP144 BN) structures are proposed. Analysis of phonon spectra, elastic constants and molecular dynamics simulation energy changes at 800 K indicates that cP128 BN and cP144 BN have dynamical stability, mechanical stability and thermodynamic stability. The bulk to shear modulus ratios for cP128 BN and cP144 BN are calculated to be 2.28 and 2.26, and the Poisson's ratios are calculated to be 0.31 and 0.31, respectively, indicating that both novel BN polymorphs are ductile. Compared with the anisotropy of cP128 BN, c-BN, P213 BN and Pm-3n BN in the primary plane, cP144 BN has large anisotropy in the primary planes. Moreover, both cP128 BN and cP144 BN are wide band gap semiconductors, in which cP128 BN has a direct band gap with a band gap of 3.297 eV, and cP144 BN can be regarded as an indirect band gap semiconductor with a band gap of 2.824 eV. Through the design and study of these two novel electronic materials, it can be found that they have good prospects for application in the industry for optoelectronic devices, as well as high temperature, high power and other electronic devices.