Theoretical dependence of hardness on the structural parameters for hard and superhard ceramics

This study presents the results of a brief overview on hard and superhard ceramic materials, in particular the crystal lattice parameters and hardness. Their structural parameters were analyzed in order to determine a theoretical dependence describing the hardness changes. A parameter of an effective volume of crystal structure was proposed, which was considered along with the crystal lattice volume and two more indices, i.e. the coordination number and the structural factor. It was shown that the structural factor was determined both for simple substances and for crystals of chemical compounds in which polyatomic molecular complexes were present. A theoretical dependence based on the fundamental relationship between hardness and the deviation of the effective volume of the crystal structure was proposed.