Predicting a novel two-dimensional BN material with a wide band gap

Based on density functional theory, a new two-dimensional boron nitride, Pmma BN, is proposed and studied in detail for the first time. The stability of Pmma BN is demonstrated using phonon spectra, ab initio molecular dynamics simulations at 300 and 500 K, and in-plane elastic constants. The orientation dependences of the Young’s modulus and Poisson’s ratio show that Pmma BN has large mechanical anisotropy. Pmma BN is an indirect band gap semiconductor material with a band gap of 5.15 eV and the hole and electron effective masses have high anisotropy. The electron carrier mobilities of Pmma BN along the x and y directions are similar, while the hole carrier mobility along the y direction is more than double that along the x direction. The band gap of Pmma BN remains indirect under the effect of uniaxial tensile strain and its adjustable range reaches 0.64 eV when the uniaxial strain is applied along the x direction. When uniaxial strain is applied along the y direction, the positions of the conduction band minimum and valence band maximum change. Pmma BN under uniaxial strain shows strong optical absorption capacity in the ultraviolet region. To explore its potential clean energy applications, the thermoelectric properties of Pmma BN are also investigated