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Shielding calculations are commonly performed on minimum energy structures of the systems under study (that is, after initial geometry optimization). In Gaussian the shielding calculations are performed for all NMR active nuclei with the "NMR" keyword as shown for the example of methane in Table 8.1.1 below. Table 8.1.1.
29 lis 2023 · Experimental studies of small molecules in the gas phase are used as reference for benchmark calculations of NMR parameters. Such studies are important for providing absolute nuclear magnetic shieldings and magnetic moments of small molecules diluted in an inert gas.
When experiments are performed at a constant magnetic field, as it is normally done in modern NMR spectrometers, a shielding effect results on a shift of the resonance to a higher frequency, Figure 2 Powder pattern spectra for symmetric and asym-metric chemical shielding tensors. From Facelli et al. (5). All values are from Mason (7).
Our calculations on O, Al, Si, P, Zn and Cd NMR shieldings, using both conventional common-origin coupled Hartree-Fock theory and the localized-orbital local-origin modification known as LORG, have reproduced many trends in both isotropic and anisotropic NMR shielding values and have, in some cases, substantiated qualitative interpretations of ...
23 lis 2020 · GIAO NMR calculations of shielding constants were conducted in THF with mPW1PW91, PBE0 and B3LYP density functionals, combined with 6-311+G(2d,p), cc-pVDZ and cc-pVTZ basis sets. Fitted empirical scaling factors from linear plots of theoretical vs. experimental boron chemical shifts were derived.
3 sty 2023 · This paper presents a systematic study of applying composite method approximations with locally dense basis sets (LDBS) to efficiently calculate NMR shielding constants in small and medium-sized molecules.
Isotropic NMR shielding constants σiso were calculated for hydrogen, carbon, nitrogen, oxygen, fluorine and phosphorous atoms in small molecules by using numerical basis functions, which were based on AOs of Discrete Variational Xα (DV-Xα) method and were modified to London atomic orbitals to avoid the gauge-origin-dependence when magnetic field...
