Use of Mo/ller-Plesset perturbation theory in molecular calculations: Spectroscopic constants of first row diatomic molecules

Journal Article · Sun Mar 01 04:00:00 EST 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.476308· OSTI ID:615376

Dunning, Jr, T H ^[1]; Peterson, K A ^[2]

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1. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington99352 (United States)
2. Department of Chemistry, Washington State University and the Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington99352 (United States)

The convergence of Mo/ller{endash}Plesset perturbation expansions (MP2{endash}MP4/MP5) for the spectroscopic constants of a selected set of diatomic molecules (BH, CH, HF, N{sub 2}, CO, and F{sub 2}) has been investigated. It was found that the second-order perturbation contributions to the spectroscopic constants are strongly dependent on basis set, more so for HF and CO than for BH. The MP5 contributions for HF were essentially zero for the cc-pVDZ basis set, but increased significantly with basis set illustrating the difficulty of using small basis sets as benchmarks for correlated calculations. The convergence behavior of the {ital exact} Mo/ller{endash}Plesset perturbation expansions were investigated using estimates of the {ital complete basis set limits} obtained using large correlation consistent basis sets. For BH and CH, the perturbation expansions of the spectroscopic constants converge monotonically toward the experimental values, while for HF, N{sub 2}, CO, and F{sub 2}, the expansions oscillate about the experimental values. The perturbation expansions are, in general, only slowly converging and, for HF, N{sub 2}, CO, and F{sub 2}, appear to be far from convergence at MP4. In fact, for HF, N{sub 2}, and CO, the errors in the calculated spectroscopic constants for the MP4 method are {ital larger} than those for the MP2 method (the only exception is D{sub e}). The current study, combined with other recent studies, raises serious doubts about the use of Mo/ller{endash}Plesset perturbation theory to describe electron correlation effects in atomic and molecular calculations. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 615376
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 12 Vol. 108; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BORON HYDRIDES
CARBON MONOXIDE
DISSOCIATION ENERGY
ELECTRON CORRELATION
ELECTRONIC STRUCTURE
FLUORINE
HYDROFLUORIC ACID
NITROGEN
PERTURBATION THEORY
SERIES EXPANSION
SPECTROSCOPIC FACTORS