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| {{TAGDEF|XC_C|[real] | 1.0 1.0 <math>\ldots</math>}} | | {{TAGDEF|XC_C|[real] | 1.0 1.0 <math>\ldots</math>}} |
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| Description: {{TAG|XC_C}} allows to specify the factors that multiply the functionals specified with the {{TAG|XC}}. | | Description: {{TAG|XC_C}} sets the factors that multiply each component of the functional specified with the {{TAG|XC}} tag. |
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| For many of the functionals implemented in the library of exchange-correlation functionals Libxc{{cite|marques:cpc:2012}}{{cite|lehtola:sx:2018}}{{cite|libxc}} it is possible to modify the parameters if one does not want to use the default values. If a functional from Libxc has parameters that can be modified, then they are listed in {{FILE|OUTCAR}} below "Parameters of Libxc functionals:" as P<math>n</math> (<math>n=1, 2, \ldots</math>). {{TAG|LIBXC1_Pn}} and {{TAG|LIBXC2_Pn}} are for the functionals called with {{TAG|LIBXC1}} and {{TAG|LIBXC2}}, respectively.
| | == Related tags and articles == |
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| An example is given below for the GGA PBE functional{{cite|perdew:prl:1996}} where the default parameters <math>\mu=0.21951</math> in exchange and <math>\beta=0.066725</math> in correlation are changed to <math>\mu=10/81\approx0.12345679</math> and <math>\beta=0.046</math> to get the PBEsol functional{{cite|perdew:prl:2008}} (of course, the simpler way to use PBEsol from Libxc would be to call it directly with {{TAG|LIBXC1}}=GGA_X_PBE_SOL and {{TAG|LIBXC2}}=GGA_C_PBE_SOL).
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| {{TAG|GGA}} = LIBXC
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| {{TAG|LIBXC1}} = GGA_X_PBE # or 101
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| {{TAG|LIBXC2}} = GGA_C_PBE # or 130
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| [[LIBXC1_Pn|LIBXC1_P2]] = 0.12345679
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| [[LIBXC2_Pn|LIBXC2_P1]] = 0.046
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| {{NB|mind|The {{TAG|ALDAX}}, {{TAG|ALDAC}}, {{TAG|AGGAX}}, {{TAG|AGGAC}}, {{TAG|AMGGAX}}, and {{TAG|AMGGAC}} tags are ignored if the Libxc functional is an exchange-correlation functional (those with a tag that contains XC)}}
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| For Libxc functionals that are the semilocal component of a hybrid functional, i.e. those with a tag that starts with HYB ({{TAG|LHFCALC}}=.TRUE. will be set automatically if such a functional is selected), the following explains how it works for the mixing and screening parameters:
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| *Mixing parameter:
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| **It is usually one of the parameters {{TAG|LIBXC1_Pn}}, and can therefore be modified.
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| **For HYB_GGA_XC_PBEH, HYB_GGA_XC_B1WC, HYB_GGA_XC_HSE03, HYB_GGA_XC_HSE06, HYB_GGA_XC_HSE12, and HYB_GGA_XC_HSE12S, the value of {{TAG|AEXX}} (even if not specified explicitly in {{FILE|INCAR}}) will be used and automatically passed to the corresponding parameter in Libxc. On the other hand, if this corresponding parameter ({{TAG|LIBXC1_Pn}}) is specified in {{FILE|INCAR}}, then it will be used (instead of {{TAG|AEXX}}), however note that it will be only for the semilocal component of the hybrid functional and not for the exact exchange that will still use {{TAG|AEXX}}.
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| **For all hybrid functionals except those listed just above, {{TAG|AEXX}} will not be considered for the semilocal component of the hybrid functional, but only for the exact exchange component. Therefore, a particular choice for the mixing parameter has to be done by specifying both {{TAG|AEXX}} (for the exact exchange) and the appropriate {{TAG|LIBXC1_Pn}} (for the semilocal component).
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| **The {{TAG|ALDAX}}, {{TAG|ALDAC}}, {{TAG|AGGAX}}, {{TAG|AGGAC}}, {{TAG|AMGGAX}}, and {{TAG|AMGGAC}} tags are ignored if the Libxc functional is an hybrid functional (those with a tag that starts with HYB).
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| *Screening parameter:
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| **It is usually one of the parameters {{TAG|LIBXC1_Pn}} if it is a screened functional, and can therefore be modified.
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| **For HYB_GGA_XC_HSE03, HYB_GGA_XC_HSE06, HYB_GGA_XC_HSE12, and HYB_GGA_XC_HSE12S, the value of {{TAG|HFSCREEN}} (even if not specified explicitly in {{FILE|INCAR}}) will be used and automatically passed to the corresponding parameter in Libxc. On the other hand, if this corresponding parameter ({{TAG|LIBXC1_Pn}}) is specified in {{FILE|INCAR}}, then it will be used (instead of {{TAG|HFSCREEN}}), however note that it will be only for the semilocal component of the hybrid functional and not for the exact exchange that will still use {{TAG|HFSCREEN}}.
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| **For all hybrid functionals except those listed just above, {{TAG|HFSCREEN}} will not be considered for the semilocal component of the hybrid functional, but only for the exact exchange component. Therefore, a particular choice for the screening parameter has to be done by specifying both {{TAG|HFSCREEN}} (for the exact exchange) and the appropriate {{TAG|LIBXC1_Pn}} (for the semilocal component).
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| == Related tags and articles ==
| | {{TAG|XC}}, |
| {{TAG|LIBXC1}}, | |
| {{TAG|LIBXC2}},
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| {{TAG|LIBXC2_Pn}},
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| {{TAG|LTBOUNDLIBXC}},
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| {{TAG|GGA}}, | | {{TAG|GGA}}, |
| {{TAG|METAGGA}}, | | {{TAG|METAGGA}}, |
| {{TAG|LHFCALC}},
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| {{TAG|AEXX}},
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| {{TAG|ALDAX}}, | | {{TAG|ALDAX}}, |
| {{TAG|ALDAC}}, | | {{TAG|ALDAC}}, |
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| {{TAG|AGGAC}}, | | {{TAG|AGGAC}}, |
| {{TAG|AMGGAX}}, | | {{TAG|AMGGAX}}, |
| {{TAG|AMGGAC}}, | | {{TAG|AMGGAC}} |
| [[list_of_hybrid_functionals|List of hybrid functionals]]
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| {{sc|LIBXC1_Pn|Examples|Examples that use this tag}} | | {{sc|XC_C|Examples|Examples that use this tag}} |
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| == References == | | == References == |
