The Spin–Spin Coupling Constants in Ethane, Methanol and Methylamine: A Comparison of DFT, MCSCF and CCSD Results

Publisher： MDPI

E-ISSN： 1422-0067|4|3|143-157

ISSN： 1422-0067

Source： International Journal of Molecular Sciences, Vol.4, Iss.3, 2003-02, pp. : 143-157

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Abstract

The spin–spin coupling constants in ethane, methylamine, and methanol have been calculated using density-functional theory (DFT), coupled-cluster singles- and-doubles (CCSD) theory, and multiconfigurational self-consistent field (MCSCF) theory so as to benchmark the performance of DFT against high-level ab initio methods and experimental data. For each molecule, the Karplus curve has been evaluated at the three computational levels. The comparisons with ab initio methods indicate that DFT reproduces the ¹J(CH), ¹J(CC), and ¹J(NH) one-bond couplings well but is less accurate for ¹J(CN), ¹J(OH), and ¹J(CO). While DFT performs well for the geminal couplings ²J(HH) and ²J(CH), it tends to overestimate the vicinal ³J(HH) couplings slightly although it is sufficiently accurate for most purposes.