The interplay of higher-order vibronic coupling and host-lattice strain in the E-2(g) ground state of copper(II) elongated or compressed octahedra?

The coordination geometry of Cu 2+ doped into the octahedral sites of solid materials may vary between tetragonally elongated and compressed, very often superimposed by distinct orthorhombic distortion components. The geometric deviation from the otherwise preferred D 4h elongation can be traced back to the presence of host-site strains due to elastic lattice properties or tiny distortions of the host polyhedra. Various examples are discussed on the basis of a simple and a more sophisticated (including dynamic features) vibronic coupling model. © 1997, R. Oldenbourg Verlag, München. All rights reserved.