Elastic moduli and brittleness of diamondlike and zinc blende structured solids

In this paper, semiempirical formulae for both bulk modulus (B in GPa) and shear modulus (G in GPa) of diamondlike and zinc blende (ANB8−N) covalent solids are elaborated in terms of nearest neighbour distance (d in Å), covalent fraction (fc) and product of ionic charges (ZaZc) of the bonding. The resulting expressions can be applied to a broad selection of covalent materials and their modulus predictions are in good agreement with the experimental data and those from ab initio calculations. Furthermore, the correlation between the ratio G/B and the aforementioned bonding parameters was investigated. The analysis of this relationship demonstrates that compared to the nearest neighbour distance (d in Å), covalent fraction (fc) and product of ionic charges (ZaZc) are predominant parameters responsible for the brittle features of covalent materials.