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.Comment: 9 pages, 4 eps figure