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ABSTRACT: Onebond spin–spin coupling constants involving selenium of seven different types, 1 J(Se,X), X = 1H, 13C, 15 N, 19 F, 29Si, 31P, and 77Se, were calculated in the series of 14 representative compounds at the SOPPA(CCSD) level taking into account relativistic corrections evaluated both at the RPA and DFT levels of theory in comparison with experiment. Relativistic corrections were found to play a major role in the calculation of 1 J(Se,X) reaching as much as almost 170% of the total value of 1 J(Se,Se) and up to 60–70% for the rest of 1 J(Se,X). Scalar relativistic effects (Darwin and massvelocity corrections) by far dominate over spin–orbit coupling in the total relativistic effects for all 1 J(Se,X). Taking into account relativistic corrections at both random phase approximation and density functional theory levels essentially improves the agreement of theoretical results with experiment. The most ‘relativistic’ 1 J(Se,Se) demonstrates a marked Karplustype dihedral angle dependence with respect to the mutual orientation of the selenium lone pairs providing a powerful tool for stereochemical analysis of selenoorganic compounds. Copyright © 2014 John Wiley & Sons, Ltd. Magnetic Resonance in Chemistry 07/2014; · 1.53 Impact Factor

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ABSTRACT: The computational study of the onebond 29Si–13C spin–spin coupling constants has been performed at the secondorder polarization propagator approximation (SOPPA) level in the series of 60 diverse silanes with a special focus on the main factors affecting the accuracy of the calculation including the level of theory, the quality of the basis set, and the contribution of solvent and relativistic effects. Among three SOPPAbased methods, SOPPA(MP2), SOPPA(CC2), and SOPPA(CCSD), the best result was achieved with SOPPA(CCSD) when used in combination with Sauer's basis set augccpVTZJ characterized by the mean absolute error of calculated coupling constants against the experiment of ca 2 Hz in the range of ca 200 Hz. The SOPPA(CCSD)/augccpVTZJ method is recommended as the most accurate and effective computational scheme for the calculation of 1J(Si,C). The slightly less accurate but essentially more economical SOPPA(MP2)/augccpVTZJ and/or SOPPA(CC2)/augccpVTZJ methods are recommended for larger molecular systems. It was shown that solvent and relativistic corrections do not play a major role in the computation of the total values of 1J(Si,C); however, taking them into account noticeably improves agreement with the experiment. The rovibrational corrections are estimated to be of about 1 Hz or 1–1.5% of the total value of 1J(Si,C). Copyright © 2014 John Wiley & Sons, Ltd. Magnetic Resonance in Chemistry 05/2014; · 1.53 Impact Factor

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ABSTRACT: Fourcomponent relativistic calculations of (77) Se(13) C spinspin coupling constants have been performed in the series of selenium heterocycles and their parent openchain selenides. It has been found that relativistic effects play an essential role in the seleniumcarbon coupling mechanism and could result in a contribution of as much as 1525% of the total values of the onebond seleniumcarbon spinspin coupling constants. In the overall contribution of the relativistic effects to the total values of (1) J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spinorbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic secondorder polarization propagator approach (CC2) with the fourcomponent relativistic density functional theory scheme is recommended as a versatile tool for the calculation of (1) J(Se,C). Solvent effects in the values of (1) J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.278.4) are next to negligible decreasing negative (1) J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of (77) Se(13) C spinspin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.10.2Hz loss of accuracy. Copyright © 2014 John Wiley & Sons, Ltd. Magnetic Resonance in Chemistry 02/2014; · 1.53 Impact Factor

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ABSTRACT: A double perturbation theory (DPT) at the second order level of approximation formalism has been applied to examine the dihedral angle dependence of the Fermicontact (FC) contribution to nuclear spinspin coupling constants. The unperturbed wave function of the ground state in DPT was approximated by the HartreeFock Slater determinant, while the excited states were treated as the single excited determinants. An analytical expression relating the FC term of vicinal protonproton spinspin coupling constants across the aliphatic single carboncarbon bond to the dihedral angle describing inner rotation around the CC bond in the tenelectron tenorbital moiety HCCH has been derived and analyzed. In particular, it has been shown that extrema of (3)J(H,H) are observed at φ = πn, n = 0, ±1, ±2,…, which provides a theoretical background of a wellknown semiempirical Karplus equation. Physical Chemistry Chemical Physics 09/2013; · 4.20 Impact Factor

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ABSTRACT: A new polarization propagator approach to indirect nuclear spinspin coupling constantans is formulated within the framework of the algebraicdiagrammatic construction (ADC) approximation and implemented at the level of the strict secondorder approximation scheme, ADC(2). The ADC approach possesses transparent computational procedure operating with Hermitian matrix quantities defined with respect to physical excitations. It is sizeconsistent and easily extendable to higher orders via the hierarchy of available ADC approximation schemes. The ADC(2) method is tested in the first applications to HF, N(2), CO, H(2)O, HCN, NH(3), CH(4), C(2)H(2), PH(3), SiH(4), CH(3)F, and C(2)H(4). The calculated indirect nuclear spinspin coupling constants are in good agreement with the experimental data and results of the secondorder polarization propagator approximation method. The computational effort of the ADC(2) scheme scales as n(5) with respect to the number of molecular orbitals n, which makes this method promising for applications to larger molecules. The Journal of Chemical Physics 07/2012; 137(4):044119. · 3.12 Impact Factor

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ABSTRACT: An earlier proposed approach to molecular response functions based on the intermediate state representation (ISR) of polarization propagator and algebraicdiagrammatic construction (ADC) approximations is for the first time employed for calculations of nonlinear response properties. The twophoton absorption (TPA) spectra are considered. The hierarchy of the first and secondorder ADC∕ISR computational schemes, ADC(1), ADC(2), ADC(2)x, and ADC(3/2), is tested in applications to H(2)O, HF, and C(2)H(4) (ethylene). The calculated TPA spectra are compared with the results of coupled cluster (CC) models and timedependent densityfunctional theory (TDDFT) calculations, using the results of the CC3 model as benchmarks. As a more realistic example, the TPA spectrum of C(8)H(10) (octatetraene) is calculated using the ADC(2)x and ADC(2) methods. The results are compared with the results of TDDFT method and earlier calculations, as well as to the available experimental data. A prominent feature of octatetraene and other polyene molecules is the existence of lowlying excited states with increased double excitation character. We demonstrate that the twophoton absorption involving such states can be adequately studied using the ADC(2)x scheme, explicitly accounting for interaction of doubly excited configurations. Observed peaks in the experimental TPA spectrum of octatetraene are assigned based on our calculations. The Journal of Chemical Physics 02/2012; 136(6):064107. · 3.12 Impact Factor