Self-consistent linear-combination-of-Gaussian-orbitals approach for polymers: Application totrans-(CH)x

A self-consistent linear-combination-of-Gaussian-orbitals (SCLCGO) method for calculating electronic properties of semiconducting crystalline polymers is presented. The method is based on the division of the electron density ρ into the sum ${\rho }_0$ of spherically symmetric atom densities compensating the nuclear charges and the neutral deformation density Δρ. ${\rho }_0$ is expanded in terms of atom-centered Gaussians and Δρ in terms of plane waves. This procedure avoids the multipole expansion, keeps the effective potential (in the local-density approximation) fully general, and allows the analytic calculation of the matrix elements between the LCGO’s. The SCLCGO energy bands and ρ are presented for the dimerized all–trans-polyacetylene chain. Close agreement with optical and x-ray photoemission spectroscopy experiments is found. The results are also compared with those of other calculations.