Editing GAUSSIAN (section)

=== NMR parameters, the chemical shift ===

The '''NMR''' keyword can be added at the command line. It predicts NMR shielding tensors and magnetic susceptibilities (HF, DFT & MP2 methods).

The '''GIAO''' method is used by default, and it is one of the recommended methods.  Usually these calculations are performed with IGLO-II basis sets, altough other basis sets can also been used.

To obtain the chemical shifts, the Isotropic Magnetic shielding (ppm) obtained from the Gaussian output, should be '''referenced to that of TMS''' (tetra-methylsilane) at the same level. i.e. at b3lyp/6-31g* basis set it is 31.92 ppm.

 δ(X) (ppm) = isotropic(TMS) – isotropic(X)