Accuracy of density fitting in calculation of two-electron repulsion integrals in periodic systems

Recently implemented approach to treat the two-electron (Coulomb) integrals in periodic systems via density fitting has been examined using Hartree-Fock calculations for model systems including trans-polyacetylene, poly(methineimine), and trans-polycyanoborane. At the moment, the exchange part of the Fock operator has been taken exact. In addition to total energies, the performance has been assessed for electron densities, main parameters of the band structure as well as for the topology of selected important bands. DZP and 6-31G** atomic orbital basis sets were combined with different auxiliary sets including standard ones optimized for molecules. For the purpose of systematic comparisons also auxiliary bases based on the correlation consistent cc-pVXZ and cc-pCVXZ hierarchies have been examined. Though these hierarchies were not designed for density fitting they perform fairly well, too, exhibiting an exponential convergence behavior with the increasing cardinal number. It is shown that for bands of chemical interest the band structure is well reproduced even with quite small auxiliary sets. (C) 2007 Wiley Periodicals, Inc.