Hybrid DFT study of electronic structure on quasi- one-dimensional halogen-bridged binuclear metal complexes (MMX)

The electronic structure of quasi-one-dimensional halogen-bridged binuclear metal complex Ni-2(dta)(4)I (dta = CH3CS2-) was investigated by hybrid density functional theory. UB3LYP was successfully applied to reproduce averaged-valence spin density wave state. The magnetic interactions between Ni dimers were estimated by calculating effective exchange integrals (J(ab)) using Ni-2(dta)(4)I dimer and tetramer models. Calculated J values were consistent with that of experimental results. The natural orbital analysis of the broken-symmetry UB3LYP solution were performed to elucidate symmetry-adapted molecular orbitals and their occupation numbers. Several chemical indices such as polyradical character and information entropy were introduced on the basis of the occupation numbers to discuss the bonding character of MMX chain. All these indices supports that Ni-2(dta)(4)I was in the strongly correlating electron system. (C) 2003 Published by Elsevier Science Ltd.