THEORETICAL-STUDY OF DIAMOND UNDER STRONG ANISOTROPIC STRESSES

Calculations are carried out using the first-principles self-consistent local-density theory of the electronic structure, the total energies and the Raman frequency of diamond under hydrostatic, [100]-, [110]- and [111]-uniaxial as well as anisotropic strains. Under hydrostatic conditions the intrinsic band gap has a positive pressure coefficient while under all other conditions this coefficient is negative. Under [100]-uniaxial strain the band gap closure occurs at 285 GPa. The two anisotropic strains investigated lead to metallization pressures of respectively 414 and 740 GPa.