ABINITIO CALCULATION OF THE DIMERIZATION IN THE HALOGEN-BRIDGED TRANSITION-METAL LINEAR-CHAIN COMPOUND PT2BR6(NH3)4

All-electron local-density-approximation electronic-structure calculations show how the ligand structure of a neutral halogen-bridged transition-metal linear-chain compound, Pt2Br6(NH3)4, Modifies the electronic structure to reduce it to an effective one-dimensional system. The dimerization and opening of the band gap is then understood on the basis of a conventional two-band Su-Schrieffer-Heeger model for isolated chains. Despite the strong pdsigma coupling between the Pt d3z2-r2 and Br p(z) orbitals along the chains, the system will not dimerize in the absence of the ligand structure.