Based on cfc carbon allotrope C 8 , novel dense hexagonal sp 3 -bonded BN polytypes (4H, 6H, 8H) and BC 2 N have been proposed from crystal chemistry and first principles. All new phases were found to be superhard, mechanically and dynamically stable, with band structures characterized by large gaps, similar to diamond. hexagonal BC 2 N (c) as functions of temperature. Experimental data for diamond and wurtzite BN are shown as gray and cyan symbols, respectively.