First-principle calculations of structural and electronic properties of rutile-phase dioxides (MO2), M = Ti, V, Ru, Ir and Sn

Abstract

First principle calculations using density functional theory (DFT) and full-potential linearized augmented plane waves (FP-LAPW) method are performed to investigate the structural and electronic properties of rutile phase titanium, vanadium, ruthenium, iridium and tin dioxides, TiO2, VO2, RuO2, IrO2, and SnO2, respectively. The exchange correlation function is described using the local density approximation (LDA) and the generalized gradient approximation (GGA). The structural parameters of the dioxides are found to be in a fair agreement with experimental values and previous calculations. TiO2 exhibits the maximum cohesive energy and RuO2 exhibits the minimum, which is opposite to the trend of pure bulk metals. Titanium dioxide in the left of the periodic table exhibits an insulating behavior with an underestimated bandgap of 2 eV. As the d-band filling increases in VO2, the energy bands shift by 3 eV from those of TiO2 to cross the Fermi level and exhibit a metallic behavior with a pseudo gap to the right of the Fermi level. The energy bands coalescence in RuO2 and IrO2 exhibiting metallic behaviors. However, for a complete filled d-band SnO2, the insulating behavior is retrieved. The distortion of the octahedrons in the rutile structure lifts the degeneracy of the eg orbitals causing further splittings.