First-principles studies of the electronic and magnetic structures and bonding properties of boron subnitride B13N2

Abstract

Rhombohedral B12 unit is viewed as a host matrix embedding linear tri-atomic arrangements of elements (E) resulting in a relatively large family of boron-rich compounds with B12{E-E-E} generic formulation. The present work focuses on boron subnitride, B13N2 that we express in present context as B12{N–B–N}. Within well established quantum density functional theory (DFT) a full study of its electronic properties is provided.Also, in view of the existence of linear triatomic arrangements in simple compounds as sodium azide NaN3, i.e. NaI{N–N–N} and calcium cyanamide, CaII{N–C–N}, we devised ScIII{N–B–N} to establish comparison with B12{N–B–N}. ScBN2 is calculated to be cohesive and possessing N–B–N isolated from ScIII with dB-N ​= ​1.33 ​Å. In B12{N–B–N} an elongated dB-N ​= ​1.43 ​Å is identified due to the bonding of N with one of the two B12 boron substructures, B1 with the formation of “3B⋯N–B–N⋯3B“-like complex accompanied by a magnetic instability. Spin polarized (SP) calculations led to the onset of magnetization on central boron with M ​= ​1μB in a stable half-ferromagnetic ground state observed from the electronic density of states (DOS). The results are backed with total energy calculations in both non-spin-polarized (NSP) and spin-polarized stabilizing the latter configuration over a broad range of volumes from M(V) plots. Further illustrative results are given with the charge densities (total and magnetic) and electron localization function (ELF). Close observations (DOS) and results (crystal parameters and magnetization magnitude) were found from complementary calculations using Hartree-Fock exchange scheme.