Electronic, thermodynamic and elastic properties of pyrite RuO₂

This paper calculates the elastic, thermodynamic and electronic properties of pyrite (Pa\bar3) RuO₂ by the plane-wave pseudopotential density functional theory (DFT) method. The lattice parameters, normalized elastic constants, Cauchy pressure, brittle--ductile relations, heat capacity and Debye temperature are successfully obtained. The Murnaghan equation of state shows that pyrite RuO₂ is a potential superhard material. Internal coordinate parameter increases with pressure, which disagrees with experimental data. An analysis based on electronic structure and the pseudogap reveals that the bonding nature in RuO₂ is a combination of covalent, ionic and metallic bonding. A study of the elastic properties indicates that the pyrite phase is isotropic under usual conditions. The relationship between brittleness and ductility shows that pyrite RuO₂ behaves in a ductile matter at zero pressure and the degree of ductility increases with pressure.