2010/08/31 by A. Eugene DePrince, DePrince, A. Eugene, David A. Mazziotti +1
Chemistry · Physics and Astronomy · #Advanced Chemical Physics Studies #Chemical Physics (physics.chem-ph) #Computational Physics (physics.comp-ph) #FOS: Physical sciences #Inorganic Fluorides and Related Compounds #Mathematical Physics (math-ph) #Quantum Physics (quant-ph) #Spectroscopy and Quantum Chemical Studies
paper · pdf · doi:10.48550/arxiv.1009.0047
openalex publication_date 2010/08/31 · openalex created_date 2022/10/03 · openalex updated_date 2026/07/28
Parametric two-electron reduced-density-matrix (p-2RDM) methods have enjoyed\nmuch success in recent years; the methods have been shown to exhibit accuracies\ngreater than coupled cluster with single and double substitutions (CCSD) for\nboth closed- and open-shell ground-state energies, properties, geometric\nparameters, and harmonic frequencies. The class of methods is herein discussed\nwithin the context of the coupled electron pair approximation (CEPA), and\nseveral CEPA-like topological factors are presented for use within the p-2RDM\nframework. The resulting p-2RDM/n methods can be viewed as a density-based\ngeneralization of CEPA/n family that are numerically very similar to\ntraditional CEPA methodologies. We cite the important distinction that the\nobtained energies represent stationary points, facilitating the efficient\nevaluation of properties and geometric derivatives. The p-2RDM/n formalism is\ngeneralized for an equal treatment of exclusion-principle-violating (EPV)\ndiagrams that occur in the occupied and virtual spaces. One of these general\ntopological factors is shown to be identical to that proposed by Kollmar [C.\nKollmar, J. Chem. Phys. 125, 084108 (2006)], derived in an effort to\napproximately enforce the D, Q, and G conditions for N-representability in his\nsize-extensive density matrix functional.\n