Nuclear magnetic resonance spin–spin coupling constants from coupled perturbed density functional theory

Abstract

For the first time, a complete implementation of coupled perturbed density functional theory ͑CPDFT͒ for the calculation of NMR spin-spin coupling constants ͑SSCCs͒ with pure and hybrid DFT is presented. By applying this method to several hydrides, hydrocarbons, and molecules with multiple bonds, the performance of DFT for the calculation of SSCCs is analyzed in dependence of the XC functional used. The importance of electron correlation effects is demonstrated and it is shown that the hybrid functional B3LYP leads to the best accuracy of calculated SSCCs. Also, CPDFT is compared with sum-overstates ͑SOS͒ DFT where it turns out that the former method is superior to the latter because it explicitly considers the dependence of the Kohn-Sham operator on the perturbed orbitals in DFT when calculating SSCCs. The four different coupling mechanisms contributing to the SSCC are discussed in connection with the electronic structure of the molecule.

Calculation of spin-densities within the context of density functional theory. The crucial role of the correlation functional

“…We note that the data material presently available is not sufficient to clearly identify the role of equal-spin and opposite-spin correlation and the balanced description of these effects by the correlation functional. Therefore, previous observations, e.g., that B3LYP performs better than BPW91 or B3PW91 in SSCC calculations, 27 are not necessarily in conflict with the results of this work.…”

“…22 and 25͒ or the hybrid XC functional B3PW91, 24͑a͒ sometimes not. These facts are documented in many research papers 26,27 and one way to approach the question of the performance of BLYP versus BPW91 ͑B3LYP versus B3PW91͒ would be to identify the electronic features of the molecules investigated and to relate them to known properties of the XC functionals under consideration.…”

Relativistic calculation of indirect NMR spin-spin couplings using the Douglas-Kroll-Hess approximation

“…31,32,41,42 Therefore, it is wise to test the performance of DFT in this case. To this end, we have employed three representative functionals: PBE ͑Ref.…”

“…Moreover, as spin and orbital perturbed states do not mix at first order, it is possible to obtain the complete linear response ͑spin plus orbital͒ with only three SCF calculations per perturbed nucleus, instead of nine needed in a standard calculation ͑six for spin and three for orbital perturbations͒. However, the lack of analytical linear response 31,32 in our relativistic code is subject to all the wellknown shortcomings of numerical differentiation.…”

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

“…This was shown for carbon-carbon coupling constants of several cyclic compounds using the recently developed decomposition of the total coupling into orbital contributions using originally proposed orbital currents and partial spin polarization (J-OC-PSP) method at the coupled perturbed density functional theory (CP-DFT) level. 102 As follows from these results, 101 a typical multipath coupling constant depends on a through-space part, two or more through-bond parts and the path-path interaction part where the latter results from steric exchange repulsion between the bond paths.…”