NMR Keyword
Last Update: 12/31/2000

This properties keyword predicts NMR shielding tensors and magnetic susceptibilities using the Hartree-Fock method, DFT methods (note, however, that no current DFT functionals include a magnetic field dependence, and so the DFT methods do not provide systematically better NMR results than Hartree-Fock), and the MP2 method. 314

NMR shielding tensors may be computed with the Continuous Set of Gauge Transformations (CSGT) method [124,125,126] and the Gauge-Independant Atomic Orbital [127,128,129,130,131]. Magnetic susceptibilities may be computed with the CSGT method. Gaussian 98 also supports the IGAIM method [125-126] (a slight variation on the CSGT method) and the Single Origin method, for both shielding tensor and magnetic susceptibilities.

Structures used for NMR calculations should have been optimized at a good level of theory. Note that CSGT calculations require large basis sets to achieve accurate results.

CSGT
Compute NMR properties using the CSGT method only.

GIAO
Compute NMR properties using the GIAO method only. This is the default.

IGAIM
Use atomic centers as gauge origins.

SingleOrigin
Use a single gauge origin. This method is provided for comparison purposes but is not generally recommended.

All
Compute properties with SingleOrigin, IGAIM, and CSGT methods.

Use Iop33(10=1) to request that the eigenvectors for the shielding tensor be included in the output.

SCF, DFT AND MP2 methods. NMR may not be combined with SCRF.

Here is an example of the default output from NMR:

Magnetic properties (GIAO method)

Magnetic shielding (ppm):
  1  C    Isotropic =    57.7345   Anisotropy =   194.4092
   XX=    48.4143   YX=      .0000   ZX=      .0000
   XY=      .0000   YY=   -62.5514   ZY=      .0000
   XZ=      .0000   YZ=      .0000   ZZ=   187.3406
  2  H    Isotropic =    23.9397   Anisotropy =     5.2745
   XX=    27.3287   YX=      .0000   ZX=      .0000
   XY=      .0000   YY=    24.0670   ZY=      .0000
   XZ=      .0000   YZ=      .0000   ZZ=    20.4233

For this molecular system, the values for all of the atoms of a given type are equal, so we have truncated the output after the first two atoms.

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