This paper presents the use of two reduced-rank representations of the two-electron repulsion integrals in coupled cluster theory: resolution of the identity (RI) and Cholesky decomposition. Both approximations provide the same form of representation for the integrals, but use auxiliary basis sets obtained from different procedures.Using RI and Cholesky decompositions in coupled cluster theory results in methods that have a slightly lower computational cost, but dramatically reduced memory requirements. The latter is especially important for overcoming the memory constraints of computers.We present an implementation of the coupled cluster method with single and double excitations (CCSD) and multiple variants of the equation-of-motion (EOM) method that use RI and Cholesky decompositions. These tools enable one to target ground and excited electronic states of systems ranging from closed-shell molecules to complex radicals.

Resolution-of-the-identity and Cholesky decompositions in coupled cluster theory for ground and excited electronic states

246th National Meeting (2013)

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