Numerical application of the coupled cluster theory with localized orbitals to polymers. I. Total correlation energy per unit cell

Abstract

The orbital invariant Møller-Plesset perturbation theory of second order (LMP2), the coupled cluster doubles theory (CCD) and its linear approximation (L-CCD) are applied to compute total correlation energies per unit cell in different polymers, using localized orbitals. The involved approximations are numerically checked against calculations with the canonical MP2 (CMP2) method. The major aim of this work is to determine numerically, whether the localization properties of Wannier functions are sufficient to make a localized orbital approximation possible or not. Calculations have been performed on hydrogen chains, water chains, polyacetylene, and polyethylene applying different atomic basis sets. Also the correlation energy as function of the geometry of some of the polymers is compared to the CMP2 results. It is found that the localization of the Wannier functions is sufficient for the application of our approximation in non-bonded chains, but not in polymers with chemically bound unit cells.