Ab initio study of structural and cohesive properties of polymers: Polyiminoborane and polyaminoborane

Abstract

Results of Wannier orbital-based Hartree–Fock and various correlated ab initio calculations using 6–31G** basis sets are reported for the two boron–nitrogen polymer systems polyaminoborane [BNH4]∞ and polyiminoborane [BNH2]∞. At the Hartree–Fock level the calculated equilibrium geometries, cohesive energies, polymerization energies, and band structures are virtually identical with those obtained from the standard Bloch orbital-based approach. Electron correlation effects on the investigated ground state properties are discussed within Mo/ller–Plesset second-order perturbation theory and coupled-cluster singles, doubles, and triples theory. For polyaminoborane no bond alternation is found in contrast to previous studies. Correlation corrections to the band structures are considered in second-order Mo/ller–Plesset perturbation theory with third-order localization diagrams included. They lead to a decrease of the fundamental gap of polyaminoborane and polyiminoborane by 40% and 51%, respectively, and reduce the band dispersions.