Accurate prediction of nuclear magnetic resonance shielding constants: An extension of the focal-point analysis method for magnetic parameter calculations (FPA-M) with improved efficiency
Previously, we have proposed a method, FPA-M, for focal-point analysis of magnetic parameter calculations [Sun et al., J. Chem. Phys. 138, 124113 (2013)], where the shielding constants at equilibrium geometries σe are calculated with the second order Møller-Plesset perturbation (MP2) approach, which...
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Veröffentlicht in: | The Journal of chemical physics 2018-11, Vol.149 (18), p.184101-184101 |
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Sprache: | eng |
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Zusammenfassung: | Previously, we have proposed a method, FPA-M, for focal-point analysis of magnetic parameter calculations [Sun et al., J. Chem. Phys. 138, 124113 (2013)], where the shielding constants at equilibrium geometries σe are calculated with the second order Møller-Plesset perturbation (MP2) approach, which are extrapolated to the complete basis set (CBS) limit and then augmented by the [σe(CCSD(T)) − σe(MP2)] difference at a valence triple-ζ (VTZ) basis set, where CCSD(T) stands for the coupled cluster singles and doubles model with a perturbative correction for triple excitations. This FPA-M(MP2) method provides satisfactory results to approach to the corresponding CCSD(T)/CBS values for elements of the first two rows in the periodic tables. A series of extensions have been explored here, which replace the MP2/CBS with the Hartree-Fock (HF)/CBS for efficiency. In particular, the [σe(CCSD(T)) − σe(MP2)] VTZ difference is replaced by a step-wise correction from the [σe(CCSD(T)) − σe(MP2)] difference at a valence double-ζ basis set plus the [σe(MP2) − σe(HF)] VTZ difference, leading to a new scheme, denoted here as FPA-M(HF′). A systematical comparison has demonstrated that the FPA-M(HF′) method provides an excellent balance between accuracy and efficiency, which makes routinely accurate calculations of the shielding constants for medium-sized organic molecules and biomolecules feasible. |
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ISSN: | 0021-9606 1089-7690 |
DOI: | 10.1063/1.5041979 |