Ab initio proposition of novel BCN3 hard material based on the intergrowth of wurtzite and pyrite-like motifs

Abstract

A novel hard material, orthorhombic BCN3 based on the intergrowth of non-centrosymmetric wurtzite CN+ and centrosymmetric pyrite BN2− motifs alike in fully characterized AlSiP3 ternary is proposed from calculations within DFT methodology. BCN3 is identified as a “nitride-dinitride” related with Zintl phases. The ground state structure exhibits significantly short interatomic distances: d(C-N) = 1.47 Å and d(N-N) = 1.43 Å as compared to d(Si-P) = 2.24 Å and d(P-P) = 2.18 Å in the phosphide, resulting into high magnitude bulk modulus obtained from E,V equation of state (EOS) with B0 = 371 GPa versus B0 = 97 GPa in the phosphide. The complete set of elastic constants complies with the mechanical stability conditions of the new system and equally produces high hardness magnitude (384 GPa). Ratio of bulk/shear modules of 0.85 characterizes a brittle material. Electronic band structures identify small indirect gap semi-conducting AlSiP3 and large band gap insulator BCN3 with direct gap ΓV-ΓC ∼ 4 eV.