Elastic and electronic properties of Pbca-BN: First-principles calculations

A fully tetrahedrally bonded boron nitride (BN) allotrope with an orthorhombic structure (Pbca-BN, space group: Pbca) was investigated by first-principles calculations. In this work, we have investigated the structural, elastic, electronic properties and elastic anisotropy of Pbca-BN by density functional theory method with the ultrasoft pseudopotential scheme in the frame of the local density approximation (LDA) and the generalized gradient approximation (GGA). From our calculations, we found that Pbca-BN has a bulk modulus of 344 GPa, a shear modulus of 316 GPa, a large Debye temperature 1734 K, a small Possion’s ratio 0.14, and the hardness of 60.1 GPa, thereby making it a superhard material with potential technological and industrial applications. Our calculations predict that Pbca-BN is mechanically stable and it is an insulator with wide band gap of 5.399 eV.