On the Usage of Locally Dense Basis Sets in the Calculation of NMR Indirect Nuclear Spin–Spin Coupling Constants: Vicinal Fluorine–Fluorine Couplings

Resolving an apparent discrepancy between theory and experiment: spin–spin coupling constants for FCCF

“…From Table 2 it can bee seen that 3 J(F-F) is large and negative at the computed geometries, but as the C-C and C-F distances (and therefore the F-F distance) decrease and approach the experimental distances, 3 …”

“…As the C-F distances increase, the F-F distance increases, and the negative PSO term decreases faster than the positive SD term. Thus, 3 …”

“…These range from −85. 4 Hz from semiempirical calculations, [1] −43.7 [2] and −21.5 Hz [3] from second-order polarization propagator approximation (SOPPA) calculations, and −25.4 Hz from an earlier equation of motion coupled cluster singles and doubles (EOM-CCSD) calculation. [4] The computed results prompted the authors of Ref.…”

“…[2] to question the assignment of the experimental spectrum of FCCF, which yielded a value of 2.1 Hz for 3 J(F-F), [5] although the sign of this coupling constant was not determined. In an effort to resolve this discrepancy, we have reinvestigated spin-spin coupling in FCCF, with emphasis on 3 …”

Atomic partition of the optical rotatory power of methylhydroperoxide

“…37͒ computational level were carried out with the DALTON program. 38 In order to keep the number of basis functions below 255, we have used a locally dense basis set, 62 where the aug-cc-pCVTZ basis set, 46 basis set 2, was used for the HO 1 O 2 moiety, but the second polarization functions were removed for the atoms in the methyl group. The MCRPA calculation was of the complete active space ͑CAS͒ type 63 with 14 electrons in 14 active orbitals ͑14,14͒ and the 1s and 2s orbitals of carbon and oxygen inactive, i.e., with one correlating orbital per occupied orbital in the active space.…”