title: A Fast Implementation of Perfect Pairing and Imperfect Pairing Using the Resolution of the Identity Approximation.
abstract: We present an efficient implementation of the perfect pairing and imperfect pairing coupled-cluster methods, as well as their nuclear gradients, using the resolution of the identity approximation to calculate two-electron integrals. The perfect pairing and imperfect pairing equations may be solved rapidly, making integral evaluation the bottleneck step. The method's efficiency is demonstrated for a series of linear alkanes, for which we show significant speed-ups (of approximately a factor of 10) with negligible error. We also apply the imperfect pairing method to a model of a recently synthesized stable singlet biradicaloid based on a planar Ge-N-Ge-N ring, confirming its biradical character, which appears to be remarkably high.
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460.
authors.forename: Alex
authors.initials: A
authors.lastname: Sodt
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460.
authors.forename: Greg J O
authors.initials: GJ
authors.lastname: Beran
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460.
authors.forename: Yousung
authors.initials: Y
authors.lastname: Jung
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460.
authors.forename: Brian
authors.initials: B
authors.lastname: Austin
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460.
authors.forename: Martin
authors.initials: M
authors.lastname: Head-Gordon