Electronic structure and physical properties of the spinel-type phase of BeP2N4from all-electron density functional calculations

Abstract

Using density-functional-theory-based ab initio methods, the electronic structure and physical properties of the newly synthesized nitride BeP{sub 2}N{sub 4} with a phenakite-type structure and the predicted high-pressure spinel phase of BeP{sub 2}N{sub 4} are studied in detail. It is shown that both polymorphs are wide band-gap semiconductors with relatively small electron effective masses at the conduction-band minima. The spinel-type phase is more covalently bonded due to the increased number of P-N bonds for P at the octahedral sites. Calculations of mechanical properties indicate that the spinel-type polymorph is a promising superhard material with notably large bulk, shear, and Young's moduli. Also calculated are the Be K, P K, P L{sub 3}, and N K edges of the electron energy-loss near-edge structure for both phases. They show marked differences because of the different local environments of the atoms in the two crystalline polymorphs. These differences will be very useful for the experimental identification of the products of high-pressure syntheses targeting the predicted spinel-type phase of BeP{sub 2}N{sub 4}.