AEXX: Difference between revisions
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Description: {{TAG|AEXX}} specifies the fraction of exact exchange in a Hartree-Fock/DFT hybrid functional type calculation. | Description: {{TAG|AEXX}} specifies the fraction of exact exchange in a Hartree-Fock/DFT hybrid functional type calculation. | ||
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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 indepently. Examples: if {{TAG|AEXX}}=0.25, 1/4 of the exact exchange is used, and 3/4 of the LDA exchange is added. For {{TAG|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 {{TAG|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 {{TAG|AGGAX}} and {{TAG|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 {{TAG|AGGAX}} and {{TAG|AGGAC}}). | |||
== Related Tags and Sections == | == Related Tags and Sections == | ||
Revision as of 16:57, 1 February 2011
AEXX = [real]
| Default: AEXX | = 0.25 | if LHFCALC=.TRUE. |
| = 0 | otherwise |
Description: AEXX specifies the fraction of exact exchange in a Hartree-Fock/DFT hybrid functional type calculation.
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 indepently. 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).