Heßelmann, Andreas:

DFT-SAPT with density fitting: a new efficient method to study intermolecular interaction energies

In: Journal of Chemical Physics, Jg. 122 (2005), S. 014103-1 - 014103-17
Zeitschriftenaufsatz / Fach: Chemie
The previously developed DFT-SAPT approach, which combines symmetry-adapted
intermolecular perturbation theory (SAPT) with a density-functional theory (DFT)
representation of the monomers, has been implemented by using density fitting
of two-electron objects. This new approach, termed DF-DFT-SAPT, scales with the
fifth power of the molecular size and with the third power upon increase of the
basis set size for a given dimer, thus drastically reducing the cost of the
conventional DFT-SAPT method. The accuracy of the density fitting approximation
has been tested for the ethyne dimer. It has been found that the errors in the
interaction energies due to density fitting are below 10$^{-3}$ kcal/mol with
suitable auxiliary basis sets and thus one or two orders of magnitude smaller
than the errors due to the use of a limited atomic orbital basis set. An
investigation of three prominent structures of the benzene dimer, namely the
T-shaped, parallel displaced and sandwich geometries, employing basis sets of
up to augmented quadruple-zeta quality shows that DF-DFT-SAPT outperforms
second-order Moller-Plesset theory (MP2) and gives total interaction
energies which are close to the best estimates infered from combining
the results of MP2 and coupled-cluster theory with single, double,
and perturbative triple excitations (CCSD(T)).

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