Exploring Alternate Methods for Calculation of High-Level Vibrational Corrections of NMR Spin-Spin Coupling Constants
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Traditional nuclear magnetic resonance (NMR) calculations typically treat systems with a Born-Oppenheimer-derived electronic wavefunction that is solved for a fixed nuclear geometry. One can numerically account for this neglected nuclear motion by averaging over property values for all nuclear geometries with a vibrational wavefunction and adding this expectation value as a correction to an equilibrium geometry property value. Presented are benchmark coupled-cluster singles and doubles (CCSD) vibrational corrections to spin-spin coupling constants (SSCCs) computed at the level of vibrational second-order perturbation theory (VPT2) using the vibrational averaging driver of the CFOUR program. As CCSD calculations of vibrational corrections are very costly, cheaper electronic structure methods are explored via a newly developed Python vibrational averaging program within the Dalton Project. Namely, results obtained with the second-order polarisation propagator approximation (SOPPA) and density functional theory (DFT) with the B3LYP and PBE0 exchange-correlation functionals are compared to the benchmark CCSD//CCSD(T) and experimental values. CCSD//CCSD(T) corrections are also combined with literature CC3 equilibrium geometry values to form the highest-order vibrationally corrected values available i.e. CC3//CCSD(T) + CCSD//CCSD(T). CCSD//CCSD(T) statistics showed favourable statistics in comparison to experimental values, albeit at an unfavourably high computational cost. A cheaper CCSD//CCSD(T) + B3LYP method showed quite similar mean absolute deviation (MAD) values as CCSD//CCSD(T), concluding that CCSD//CCSD(T) + B3LYP is optimal in terms of cost and accuracy. With reference to experimental values, a vibrational correction was not worth the cost for all other methods tested. Finally, deviation statistics showed that CC3//CCSD(T) + CCSD//CCSD(T) vibrational corrected equilibrium values deteriorated in comparison to CCSD//CCSD(T) attributed to the use of a smaller basis and/or lack of solvation effects for the CC3 equilibrium calculations.
Originalsprog | Engelsk |
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Tidsskrift | Journal of Chemical Theory and Computation |
Vol/bind | 20 |
Udgave nummer | 3 |
Sider (fra-til) | 1228–1243 |
Antal sider | 16 |
ISSN | 1549-9618 |
DOI | |
Status | Udgivet - 1 feb. 2024 |
ID: 378872010