期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 109, 期 40, 页码 9183-9192出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp053780c
关键词
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The perfect pairing (PP) approximation from generalized valence bond theory is formulated in an unrestricted fashion for both closed- and open-shell systems using a coupled cluster ansatz. In the model chemistry proposed here, active electron pairs are correlated, but the unpaired or radical electrons remain uncorrelated, leading to a linear number of decoupled cluster amplitudes which can be solved for analytically. The alpha and beta spatial orbitals are variationally optimized independently. This minimal treatment of electron -electron correlation noticeably improves upon symmetry-breaking problems and other pathologies in Hartree-Fock (HF) theory and may be computed using the resolution of the identity approximation at only a factor of several times more effort than HF itself. PP also generally predicts improved molecular structures over HE This compact, correlated wave function potentially provides a useful starting point for dynamical correlation corrections.
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