Optical and electronic properties of Ru[O.sub.2] from first principles

The systematic trends of electronic structure and optical properties of Ru[O.sub.2] 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 -10 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 Ca[Cl.sub.2]-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. PACS Nos: 63.20.dk, 71.20.-b, 78.20.Ci Nous utilisons un pseudo-potentiel a norme conservee dans l'approximation du gradient generalise pour obtenir le potentiel d'echange-correlation, afin d'etudier les tendances systematiques de la structure electronique et des proprietes optiques du Ru[O.sub.2], incluant ses quatre phases. La densite totale d'etats (DOS) et la structure de la bande d'energie revelent que la phase fluorite possede la plus grande largeur de bande de valence (0-30 eV) et que la phase pyrite possede la plus etroite (-20-0 eV). Etudiant les DOS partielles, nous trouvons que les electrons 2p de O dans la phase fluorite montrent un deplacement marque vers le niveau de Fermi, alors que les electrons s et p du Ru dans la phase rutile contribuent peu aux niveaux d'energie orbitaux. Pour la premiere fois, nous trouvons que le pseudo-potentiel a norme conservee echoue a obtenir la DOS normale et les distributions de bande d'energie pour le Ru rutile sous -10 eV, alors que de telles distributions sont obtenues avec succes a partir de pseudo-potentiels ultra mous. Etudiant les proprietes optiques, nous trouvons que les phases rutile et du type Ca[Cl.sub.2] sont plus proches et que la phase fluorite a la reponse la plus sensible sur toute la region de reaction radiative. La fonction de perte d' energie electronique revele que la phase pyrite a la plus faible intensite relative. [Traduit par la Redaction]
1. Introduction The low resistivity and reactivity of Ru[O.sub.2] has made it technologically important as a strip-line conductor in integrated circuits, as a diffusion barrier in contact metallizations, etc. [1, [...]