Density fitting (DF) techniques are used to approximate all electron repulsion integrals (ERIs) required for computations with coupled cluster through perturbative triple excitations [CCSD(T)]. Three-index integrals can be obtained from standard auxiliary basis sets optimized for second-order perturbation theory (DF-MP2) or a partial Cholesky decomposition of the 4-index ERI tensor. We explore the efficacy of Cholesky or singular value decompositions of the 4-virtual ERI tensor in the molecular orbital basis to accelerate its contraction with the coupled cluster amplitudes. We demonstrate the accuracy of DF-CCSD(T) by computing interaction energies for the S22 test set. DF techniques introduce very modest errors, typically amounting to only a few hundredths of one kcal/mol.

Density fitting techniques for coupled cluster theory computations of noncovalent interactions

245th National Meeting (2013)

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