Second-order Polarization Propagator Approximation Calculations

2 Second-Order Polarization Propagator Approximation Calculations. - 

Krivdin performed a systematic study of the one-bond and long-range J(C, C), J(C, H), and J(H, H) coupling constants in the series of nine bicycloalkanes at the 

Krivdin and Kuznetsova carried out an ab initio calculation for spin-spin coupling constants in a series of saturated three- and four-membered heterocycles within a framework of second-order perturbation theory using SOPPA. It was shown that the main variations in the Jf C, C) coupling constants in the heterocycle series under study are governed by the FC contribution and that the FC contribution is highly sensitive to the heteroatom character 

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Empirical equilibrium coupling constants can be compared as a benchmark with calculated equilibrium coupling constants obtained with various methods. A comparison of these empirical equilibrium constants with calculated equilibrium constants suggested that the restricted-active-space self-consistent field (RASSCF) method is the best approach for calculating the indirect nuclear spin-spin coupling constants of small molecules, and that the second-order polarization propagator approximation (SOPPA) and DFT are similar in performance. 

The paramagnetic contribution is more demanding to calculate and is a bit more sensitive to electron correlation, although not a great deal. For instance, for ammonia, the RPA (effectively uncorrelated) value is 38.45 ppm a.u., while the Second Order Polarization Propagator Approximation (correlated) yields 38.15 ppm a.u. 

Enevoldsen, T., Oddershede, J., Sauer, S. P. A. (1998). Correlated calculations of indirect nuclear spin-spin coupling constants using second-order polarization propagator approximations SOPPA and SOPPA(CCSD). Theoretical Chemistry Accounts, 100, 275. 

The computational study of the one-bond carbon-silicon couplings has been performed at the second-order polarization propagator approximation (SOPPA) level by Rusakova et oZ. in a series of 60 various silanes and compared with the experimental Vcsi values taken from the literature. A special attention has been paid by the authors to the main factors affecting the accuracy of the calculation including the level of theoiy, the quality of the basis set, and the contribution of solvent and relativistic effects. The reported in the paper values have been obtained at the SOPPA(CC2) level, whereas for the calculations of solvent and... 

Electric moments, polarizabilities, and hyperpolarizabilities for BH were calculated for the first time [23], as were field and field gradient polarizabilities [24]. Spectroscopic properties were calculated for BH using the coupled electron pair approximation. The potential curve for BH was calculated at 22 points and Rq was found to be 1.23115 A and p to be 1.244 D [21]. The radiative lifetime of the A state of BH was calculated from second-order polarization propagator calculations [25], and the singlet-triplet separation in BH was calculated using ab initio MO methods. The latter, described as the singlet-triplet separation, was found to be 31.9 kcal/mol [26]. Finally, the possible dynamical pathways in the system BH + H+ were probed [27]. 

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