Hartree-Fock calculations for the electronic and lattice structures in heavily sodium doped polyacetylene

Abstract

We evaluated 3D interactions in highly Na-doped polyacetylene, (CH) x, reasonably based on the structure reported in an X ray experiment. Interchain transfers (ICTs) via dopants estimated quantum chemically are found to reach up to 0.93 eV and spread over five sites on each adjacent chain at doping concentration, 11.1%, Screened Coulomb interactions are evaluated as Thomas-Fermi potential for quasi ID conductors numerically, to estimate reasonable interchain Coulomb (ICC) and dopants' Coulomb (DC) potentials. As the intrachain Hamiltonian, SSH+extended Hubbard model is used. The Hartree-Fock (HF) ground state with geometry optimization is soliton lattices out-of-phase ordered. The gap little depends on chain length and is extrapolated to 1.3eV in infinite chain limit. So rather large ICT in itself cannot lead to metallic state in HF approximation, and electron correlation seems to be important.