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<tt>*_pv</tt> or <tt>*_sv</tt> POTCARs) as well as explicit inclusion of augmentation channel(s) with ''d''-projectors.
<tt>*_pv</tt> or <tt>*_sv</tt> POTCARs) as well as explicit inclusion of augmentation channel(s) with ''d''-projectors.


To convert the ''V''<sub>zz</sub> values into the ''C''<sub>q</sub> often encountered in NMR literature one has to specify the nuclear quadrupole moment by means of the {{TAG|QUAD_EFG}}-tag.
To convert the ''V''<sub>zz</sub> values into the ''C''<sub>q</sub> often encountered in NMR literature, one has to specify the nuclear quadrupole moment by means of the {{TAG|QUAD_EFG}}-tag.


== Related Tags and Sections ==
== Related Tags and Sections ==

Revision as of 01:37, 4 December 2012

LEFG = .TRUE. | .FALSE.
Default: LEFG = .FALSE. 

Description: compute the electric field gradients at positions of the atomic nuclei.


For LEFG=.TRUE., the electric field gradient tensors at the positions of the atomic nuclei are calculated using the method of Petrilli et al.[1]

The EFG tensors are symmetric. The principal components Vii and asymmetry parameter η are printed for each atom. Following convention the principal components Vii are ordered such that:

The asymmetry parameter η=(Vyy-Vxx)/Vzz. For so-called "quadrupolar nuclei", i.e., nuclei with nuclear spin I>1/2, NMR experiments can access Vzz and η.

Beware: Attaining convergence can require somewhat smaller EDIFF than the default of 1.e-4 and somewhat larger cutoff ENCUT than default with PREC=A. Moreover, the calculation of EFGs typically requires high quality PAW data sets. Semi-core electrons can be important (check with *_pv or *_sv POTCARs) as well as explicit inclusion of augmentation channel(s) with d-projectors.

To convert the Vzz values into the Cq often encountered in NMR literature, one has to specify the nuclear quadrupole moment by means of the QUAD_EFG-tag.

Related Tags and Sections

QUAD_EFG

References


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