First-principle study of structural and mechanical properties of hexagonal polytypes of diamond

Abstract

The values of unit-cell parameters; C-C bond lengths; elastic constants c ij and s ij ; elastic moduli B, G, and E; and hardnesses and cohesion energies have been calculated for hexagonal diamond polytypes 2H, 4H, 6H, and 8H within the approximation of density functional theory. The anisotropy of elastic moduli and hardness is investigated. It is found that the linear compressibility and hardness of polytypes in the basal plane exceeds that along the hexagonal c axis. It is shown that the difference in the anisotropic properties along and perpendicular to the hexagonal axis may be related to the specific features of polytype structure.