First-Principles Study of 30H-BN Polytypes

We calculated the electronic and lattice properties of 30H-BN which are sp(3)-bonded compounds The 30H polytype has various over 6000000 structures Their possible symmetries and hexagonalmes (H[%]) are P6(3)mc and P3ml and 6 7%similar to 93 3% respectively Hexagonality is a ratio of the number of hexagonal (h) character and the total number of cubic (c) and h characters in a unit cell Two structures in the 30H polytype are considered in this study Their stacking sequences (ABC notation) are ABCABCABCABCABCACBACBACBACBACB (P6(3)mc, H = 6 7%) and ABCBCBCBCBCBCBCBCBCBCBCBCBCBCB (P3ml, H = 93 3%) Their lattico properties were optimized automatically by the total energy pseudopotential method Calculated total energies of 30H-BN are in the order of ABCABCABCABCABCACBACBACBACBACB (6 7%) < ABCBCBCBCBCBCBCBCBCBCBCBCBCBCB (93 3%) Values in parentheses are hexagonaliues (%) This means the former is energetically more favorable than the latter The total energy of the BN polytype increases with increasing hexagonality We calculated their electronic band structures the band gap values the ale-rice band maximum (VBM) and conduction band minimum (CBM) Their electronic band structures are non metallic and band gaps are indirect [doi 10 2320/matertrans MAW201004]