The mechanism of the rutile-to-CaCl2 phasetransition: RuO2 and β-PtO2

Abstract

Using the full-potential linearized augmented-plane-wave (FLAPW)method, the mechanism of the rutile-CaCl2 phase transitionof RuO2 and the phase stability of β-PtO2are investigated. The local density functional calculations predictquantities such as lattice constants, bulk moduli, and phononfrequencies in good agreement with experiment. The pressure-inducedphase transition in RuO2 appears to be driven by the strongrepulsion between O-O and Ru-O along the diagonal direction in thexy-plane. By contrast, a strong hybridization between the Pt 5dand O 2p states is responsible for the stability of the β-PtO2 structure, for which a pseudo-gap (instead of the strongpeak for the rutile-PtO2) is opened at the Fermi level dueto the rotation of the PtO6 octahedra.