Electronic and optical properties of RuO2 and IrO2

We report first principles self-consistent electronic structure calculations of RuO2 and IrO2 using the full-potential linearized augmented plane wave method. Our electronic properties are in good agreement with x-ray photoelectron spectroscopy data regarding the bandwidths and peak positions. Additionally, we probe our electronic structures by calculating the dielectric functions and comparing them with optical measurements. Our calculations show that intraband transitions play an important role to describe properly the optical response of RuO2 and IrO2. We find that these materials are good absorbers at low energies where the dielectric functions exhibit a Drude like behavior. At higher energies, the optical features are due to electronic transitions from oxygen 2p to metal d bands. Our results for the dielectric functions and energy loss spectra show a good agreement with optical measurements.