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, C8−xBx (x = 1, 2, 3, 4), C7−xBNx (x = 1, 2, 3) and C6−xBNOx (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 C7B and C6BN were mechanically and dynamically stable compounds with potential ultra-hard characteristics, C6BN 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. Keywords: Ultra-hard material, Elastic constants, Density functional theory