Search results
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.
Shielding in NMR Structural features of the molecule will have an effect on the exact magnitude of the magnetic field experienced by a particular nucleus. This means that H atoms which have different chemical environments will have different chemical shifts.
In general, shielding effects are associated with diamagnetic effects from spherical charge distributions, whereas de-shielding effects are associated with a nonspherical charge dis-tribution originating from p or higher angular momen-tum electrons.
23 lis 2020 · In addition, the NMR shielding of the O atom, directly involved in the bond, increases, and an opposite effect is observed for C and N atoms. Linear changes between MP2/aug-cc-pVDZ calculated interaction energies and changes in NMR shielding of O, N and C atoms of NMA were reported.
29 lis 2023 · As previously, the chapter concentrates on theoretical calculations of nuclear shielding parameters and/or chemical shifts in case of free molecules in the gas phase and solution, and in some cases in the solid state using a periodic formulation.
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...
In this tutorial we look at 4-component relativistic calculations of NMR shielding constants. For best results we recommend to use the scheme of simple magnetic balance (sMB) in conjunction with London orbitals [Olejniczak2012].
