Octahedral Tilting in ACu3Ru4O12 (A=Na,Ca,Sr,La,Nd)

The perovskite-like compounds ACu3Ru4O12 (A=Na,Ca,Sr,La,Nd) are studied by means of density functional theory based electronic structure calculations using the augmented spherical wave (ASW) method. The electronic properties are strongly influenced by covalent type bonding between transition metal d and oxygen p states. The characteristic tilting of the RuO6 octahedra arises mainly from the Cu--O bonding, allowing for optimal bond lengths between these two atoms. Our results provide a deeper understanding of octahedral tilting as a universal mechanism, applicable to a large variety of multinary compounds.