ADDGRID: Difference between revisions
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Revision as of 11:14, 7 March 2019
ADDGRID = .TRUE. | .FALSE.
Default: ADDGRID = .FALSE.
Description: ADDGRID determines whether an additional support grid is used for the evaluation of the augmentation charges.
When ADDGRID=.TRUE. VASP uses an additional support grid for the evaluation of the augmentation charges. This grid contains 8 times more points than the standard "fine" grid (NGXF×NGYF×NGZF). Whenever terms involving augmentation charges are evaluated, this additional grid is used. For instance: The augmentation charge is evaluated first in real space on this additional grid, FFT-transformed to reciprocal space and then added to the total charge density on the standard "fine" grid (NGXF×NGYF×NGZF). The additional grid helps to reduce the noise in the forces significantly. In many cases, it even allows to perform calculations in which NGXF=NGX etc. The latter can be achieved by setting:
ENAUG=1 ; ADDGRID=.TRUE.
in the INCAR file. The flag can also be used for US-PPs, in particular, to reduce the noise in the forces.