First-principles calculations of electronic properties of P(6)over-bar-Si3N4 and P(6 ')over-bar-Si3N4 under pressure

Using first-principles computations, the structural, electronic properties of P (6) over bar- and P (6') over bar -Si3N4 in the pressure ranges of 40-50 GPa were investigated systematically, and the band structures and density of states have been analyzed in detail. the results show both P (6) over bar- and P (6') over bar -Si3N4 are insulators, and there have no structural phase transformation under the pressure 40-50GPa.