LEFG: Difference between revisions
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{{TAGDEF|LEFG|.TRUE. {{!}} .FALSE. | .FALSE.}} | {{TAGDEF|LEFG|.TRUE. {{!}} .FALSE. | .FALSE.}} | ||
Description: The {{TAG|LEFG}} Computes the {{TAG|Electric Field Gradient}} | Description: The {{TAG|LEFG}} Computes the {{TAG|Electric Field Gradient}} at positions of the atomic nuclei. | ||
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For {{TAG|LEFG}}=.TRUE., the electric field gradient tensors at the positions of the atomic nuclei are calculated using the method of Petrilli ''et al.''<ref name="petrilli:prb:98"/> | For {{TAG|LEFG}}=.TRUE., the electric field gradient tensors at the positions of the atomic nuclei are calculated using the method of Petrilli ''et al.''<ref name="petrilli:prb:98"/> | ||
Revision as of 13:40, 27 January 2017
LEFG = .TRUE. | .FALSE.
Default: LEFG = .FALSE.
Description: The LEFG Computes the Electric Field Gradient 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.