Optical and electronic properties of RuO2 from first principles

Abstract

The systematic trends of electronic structure and optical properties of RuO2 consisting of its four phases have been studied by using norm-conserving pseudopotential within the generalized gradient approximation for the exchange–correlation potential. The total density of states (DOS) and energy band structure investigations revealed that the fluorite phase possesses the broadest conduction bandwidth (0–30 eV) and the pyrite phase possesses the narrowest conduction bandwidth (0–5 eV). Study on partial DOS we found that O 2p electrons of the fluorite phase present a significant shift towards the Fermi level and Ru s and p electrons of the rutile phase contribute little to the orbital energy level formation. For the first time, we found that the norm-conserving pseudopotential failed to obtain the normal DOS and energy band distributions for a rutile Ru atom below about –40 eV, whereas such missing electronic distributions could be obtained successfully using an ultrasoft pseudo potential. Investigations on the optical properties further found that the rutile and CaCl2-type phases behave more similarly and the fluorite phase shows the most sensitive response in the whole radiation reaction region. The electron energy loss function revealed that the pyrite phase corresponds to the least relative intensity.