Indirect nuclear spin–spin coupling constants from multiconfiguration linear response theory

Abstract

We have used multiconfiguration self-consistent-field theory to determine indirect nuclear spin–spin coupling constants. The Fermi contact, spin dipole, and paramagnetic spin–orbit contributions are evaluated as multiconfiguration linear response functions at zero frequency and the diamagnetic spin–orbit contribution as an average value of the multiconfiguration wave function. Sample calculations on HD and CH4 demonstrate that most of the correlation contributions can be recovered in relatively small complete active space (CAS) reference state calculations.

Solvent Effects on the Indirect Spin–Spin Coupling Constants of Benzene: The DFT-PCM Approach

“…The derivatives of the variational parameters λ S and λ T with respect M L are obtained by solving the response equations [11,35] …”

“…The triplet nature of the Fermi-contact and the spin-dipolar operators means that ordinary spin-restricted approaches such as Hartree-Fock fails completely, often giving results that are several order of magnitudes too large as well as having incorrect signs [7,8]. The problem of triplet instabilities is often quite efficiently solved by introducing electron correlation, and several successful studies using multiconfigurational self-consistent field (MCSCF) [7,[9][10][11] or coupled-cluster [12][13][14] wave functions have been presented. An alternative approach has used the second-order polarization propagator approximation (SOPPA) [2,15].…”

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

“…[14]. The calculations of the spin-spin coupling constants at the MCSCF level [5,20] have been carried out by means of dalton 1.2 [19]. The restricted active-space (RAS) approach has been employed, with the nonhydrogen 1s orbitals in the inactive subspace and with the seven Hartree-Fock-occupied valence orbitals in the RAS2 subspace.…”

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 8—Monocycloalkanes

“…Geometric optimizations at DFT level were performed with GAMESS code 120 and all calculations of spin-spin coupling constants at RPA and SOPPA were carried out using the DALTON package, 9,11,121,122 whereas the SOPPA(CCSD) results were obtained with a modified version of the Dalton package. 10,11,30 Both codes, GAMESS and DALTON, were compiled as LFS (Large Files System) versions for Linux.…”