2009/06/19 by Timothy J. Lee, Peter R. Taylor · 16 citations
Physics and Astronomy · Chemistry · #Advanced Chemical Physics Studies #Spectroscopy and Quantum Chemical Studies #Molecular spectroscopy and chirality
paper · doi:10.1002/qua.560360824
It was recently proposed that the Euclidian norm of the t1 vector of the coupled-cluster wave function (normalized by the number of electrons included in the correlation procedure) could be used to determine whether a single-reference-based electron correlation procedure is appropriate. This diagnostic T1 is defined for use with self-consistent-field molecular orbitals and is invariant to the same orbital rotations as the coupled-cluster energy. T1 is investigated for several different chemical systems which exhibit a range of multireference behavior and is shown to be an excellent measure of the importance of nondynamical electron correlation and is far superior to C0 from a singles and doubles configuration interaction wave function. It is further suggested that when the aim is to recover a large fraction of the dynamical electron correlation energy, a large T1 (i.e., >0.02) probably indicates the need for a multireference electron correlation procedure.