AGGAX

AGGAX = [real]
Default: AGGAX = 1.0-AEXX if LHFCALC=.TRUE. or 1.0 if LHFCALC=.FALSE.

Description: AGGAX is a parameter that multiplies the GGA correction in the GGA exchange.

The sum of the fraction of the exact exchange and LDA exchange is always 1.0, and it is not possible to set the amount of LDA exchange independently. Examples: if AEXX=0.25, 1/4 of the exact exchange is used, and 3/4 of the LDA exchange is added. For AEXX=0.5, half of the exact exchange is used, and one half of the LDA exchange is added.

The amount of LDA correlation included in the hybrid functional can be specified through the ALDAC-tag.

The amount of gradient correction to the exchange and the correlation contributions can be set indepently, however (some popular hybride functionals for instance use only 0.8 of the gradient contribition to the exchange). The GGA flags AGGAX and AGGAC are only used if GGA is already selected (for LDA type calculations no gradient correction will be added regardless of values is used for AGGAX and AGGAC).

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