Study of ultra-hard materials of the B-C-N-O quaternary system

Abstract A number of potentially ultra-hard materials are examined using ab-initio methods. Compound phases of varying lattice stoichiometry in the B-C-N-O quaternary system, in the forms, C 8− x B x ( x  = 1, 2, 3, 4), C 7− x BN x ( x  = 1, 2, 3) and C 6− x BNO x ( x  = 1, 2) are proposed as possible ultra-hard materials with useful applications. Cell structures and elastic properties are studied, systematic trends are established. It was determined that C 7 B and C 6 BN were mechanically and dynamically stable compounds with potential ultra-hard characteristics, C 6 BN being the harder of the two. Since diamond is experimentally well understood as an ultra-hard material, we use it as a standard for comparing our results.