title: Density fitting of two-electron integrals in extended systems with translational periodicity: the Coulomb problem.
abstract: Density fitting approach to Coulomb integrals for infinite systems with translational periodicity is reformulated in direct space. Despite of the Coulomb infinite decay of some integrals, direct-space calculation is shown to be feasible. Moreover, we show that the direct-space ansatz is completely equivalent to our previous formulation in reciprocal space. Computational demands scale linearly with the number of unit cells. In addition, direct-space treatment has some practical advantages over the reciprocal-space formulation. The efficiency of our scheme is demonstrated on systems with translational periodicity in one dimension. Computation time takes only a small fraction of the conventional calculation with exact integrals. We show that for infinite systems auxiliary basis sets of equally good quality as for molecules can be constructed in a systematic way.
authors.affiliation: Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava, Slovakia. stefan.varga@savba.sk
authors.forename: Stefan
authors.initials: S
authors.lastname: Varga
authors.forename: Matús
authors.initials: M
authors.lastname: Milko
authors.forename: Jozef
authors.initials: J
authors.lastname: Noga