LFOCKSTD - Revision history

Csheldon at 09:05, 29 January 2026

2026-01-29T09:05:11Z

← Older revision		Revision as of 09:05, 29 January 2026
Line 7:		Line 7:
	This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.		This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.

	VASP typically employs shape restoration (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}) to calculate the RPA correlation energy and the exact exchange energy during RPA/GW calculations. However, this results in significant noise in the exact exchange energy and its nuclear gradients. To mitigate this issue, the {{TAG\| LFOCKSTD}} option was introduced, forcing VASP to use the standard HF treatment for the exact exchange while continuing to use shape restoration for the correlation energy. This reduces the noise in energies and RPA forces, and it leads to an exact exchange energy that is fully compatible with the exact exchange energy in standard HF calculations. This means that the energy " HF-free energy FHF" in RPA calculations is identical to the "free energy TOTEN " when reading the WAVECAR file and performing a single-step total energy evaluation ( ALGO = Eigenval; ~~LFHCALC~~ = .TRUE. ; AEXX = 1.0 ; NELM = 1). In other words, when using LFOCKSTD in RPA calculations, the exact exchange energy is fully compatible with the stepwise evaluation explained here: [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].		VASP typically employs shape restoration (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}) to calculate the RPA correlation energy and the exact exchange energy during RPA/GW calculations. However, this results in significant noise in the exact exchange energy and its nuclear gradients. To mitigate this issue, the {{TAG\| LFOCKSTD}} option was introduced, forcing VASP to use the standard HF treatment for the exact exchange while continuing to use shape restoration for the correlation energy. This reduces the noise in energies and RPA forces, and it leads to an exact exchange energy that is fully compatible with the exact exchange energy in standard HF calculations. This means that the energy <code>HF-free energy FHF</code> in RPA calculations is identical to the <code>free energy TOTEN</code> when reading the WAVECAR file and performing a single-step total energy evaluation ( {{TAG\|ALGO}} = Eigenval; {{TAG\|LHFCALC}} = .TRUE. ; {{TAG\|AEXX}} = 1.0 ; {{TAG\|NELM}} = 1). In other words, when using LFOCKSTD in RPA calculations, the exact exchange energy is fully compatible with the stepwise evaluation explained here: [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].

	It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.~~5.2~~.		It is strongly recommended to activate {{TAG\|LFOCKSTD}} for all GW and RPA calculations starting from version 6.6.0

	Note that VASP uses one-center terms to correct the exact exchange energy for the difference in shape between all-electron and pseudo orbitals. Therefore, shape restoration is neither required nor beneficial for the exact exchange term (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}).		Note that VASP uses one-center terms to correct the exact exchange energy for the difference in shape between all-electron and pseudo orbitals. Therefore, shape restoration is neither required nor beneficial for the exact exchange term (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}).

Csheldon at 09:01, 29 January 2026

2026-01-29T09:01:26Z

← Older revision		Revision as of 09:01, 29 January 2026
Line 4:		Line 4:
	Description: {{TAG\|LFOCKSTD}} applies to RPA and GW calculations. It forces VASP to evaluate the exact exchange fully consistent with the standard treatment in HF calculations.		Description: {{TAG\|LFOCKSTD}} applies to RPA and GW calculations. It forces VASP to evaluate the exact exchange fully consistent with the standard treatment in HF calculations.
	----		----
	{{NB\|~~mind\|Avaliable as of~~ 6.~~5.2~~.}}		{{Available\|6.6.0}}
	This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.		This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.

Kresse: Second round of grammar and spell checking and

2025-07-04T12:21:13Z

Second round of grammar and spell checking and

← Older revision		Revision as of 12:21, 4 July 2025
Line 7:		Line 7:
	This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.		This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.

	VASP ~~usually uses~~ shape restoration (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}) ~~for~~ the RPA correlation energy and ~~the evaluation of~~ the exact exchange during RPA/GW calculations. However, this results in significant noise in the exact exchange energy and its nuclear gradients. To mitigate this, LFOCKSTD was introduced, forcing VASP to use the standard HF treatment for the exact exchange while continuing to use shape restoration for the correlation energy. This reduces the noise in energies and RPA ~~force~~ and leads to an exact exchange energy that is fully compatible with the exact exchange energy in standard HF calculations. This means that the energy " HF-free energy FHF" in RPA calculations is identical to the "free energy TOTEN " when reading the WAVECAR file and performing a single-step total energy evaluation ( ALGO = Eigenval; LFHCALC = .TRUE. ; AEXX = 1.0 ; NELM = 1). In other words, using LFOCKSTD in ~~the~~ RPA, the exact exchange energy is fully compatible with the stepwise evaluation explained here: [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].		VASP typically employs shape restoration (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}) to calculate the RPA correlation energy and the exact exchange energy during RPA/GW calculations. However, this results in significant noise in the exact exchange energy and its nuclear gradients. To mitigate this issue, the {{TAG\| LFOCKSTD}} option was introduced, forcing VASP to use the standard HF treatment for the exact exchange while continuing to use shape restoration for the correlation energy. This reduces the noise in energies and RPA forces, and it leads to an exact exchange energy that is fully compatible with the exact exchange energy in standard HF calculations. This means that the energy " HF-free energy FHF" in RPA calculations is identical to the "free energy TOTEN " when reading the WAVECAR file and performing a single-step total energy evaluation ( ALGO = Eigenval; LFHCALC = .TRUE. ; AEXX = 1.0 ; NELM = 1). In other words, when using LFOCKSTD in RPA calculations, the exact exchange energy is fully compatible with the stepwise evaluation explained here: [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].

	It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.5.2.		It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.5.2.

	Note that VASP uses one-center terms to correct the exact exchange energy for the difference in shape between all-electron and pseudo orbitals. Therefore, shape restoration is ~~not~~ required or beneficial for the exact exchange term (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}).		Note that VASP uses one-center terms to correct the exact exchange energy for the difference in shape between all-electron and pseudo orbitals. Therefore, shape restoration is neither required nor beneficial for the exact exchange term (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}).
	== Related tags and articles ==		== Related tags and articles ==
	{{TAG\|LRPAFORCE}}		{{TAG\|LRPAFORCE}}

Kresse: Imroved wording and spell checking

2025-07-04T12:17:34Z

Imroved wording and spell checking

← Older revision		Revision as of 12:17, 4 July 2025
Line 7:		Line 7:
	This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.		This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.

	~~Usually~~ VASP uses shape restoration (see NMAXFOCKAE and LMAXFOCKAE) for the RPA correlation ~~contributions as well as for~~ the evaluation of the exact exchange during RPA/GW calculations. ~~This however~~ results in ~~signficant~~ noise ~~which is particularly pronounced for~~ the exact exchange. To mitigate this ~~issue~~, LFOCKSTD was introduced~~: it forces~~ VASP to use the standard HF-treatment for the exact exchange~~, but continues~~ to use shape restoration for the correlation ~~contributions~~. This ~~not only~~ reduces the noise in ~~the~~ force~~, but also~~ leads to an exact exchange energy that is fully compatible ~~wiht~~ the exact exchange ~~contribution~~ in standard HF calculations (that is the energy " HF-free energy FHF" in ~~the~~ RPA calculations is ~~idential~~ to the "free energy TOTEN " ~~for~~ when reading the WAVECAR file and performing a single step total energy ~~calculation~~ ( ALGO = Eigenval; LFHCALC = .TRUE. ; AEXX = 1.0 ; NELM = 1). ~~This means that this restores~~ the ~~agreement of <code>FHF</code>~~ with the ~~result obtained in the~~ [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].		VASP usually uses shape restoration (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}) for the RPA correlation energy and the evaluation of the exact exchange during RPA/GW calculations. However, this results in significant noise in the exact exchange energy and its nuclear gradients. To mitigate this, LFOCKSTD was introduced, forcing VASP to use the standard HF treatment for the exact exchange while continuing to use shape restoration for the correlation energy. This reduces the noise in energies and RPA force and leads to an exact exchange energy that is fully compatible with the exact exchange energy in standard HF calculations. This means that the energy " HF-free energy FHF" in RPA calculations is identical to the "free energy TOTEN " when reading the WAVECAR file and performing a single-step total energy evaluation ( ALGO = Eigenval; LFHCALC = .TRUE. ; AEXX = 1.0 ; NELM = 1). In other words, using LFOCKSTD in the RPA, the exact exchange energy is fully compatible with the stepwise evaluation explained here: [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].

	It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.5.2.		It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.5.2.

	~~In earlier versions,~~ one-center ~~density contributions of EXX can be treated only with~~ shape and ~~electrostatic multipole reconstruction using~~ {{TAG\|LMAXFOCKAE}}.		Note that VASP uses one-center terms to correct the exact exchange energy for the difference in shape between all-electron and pseudo orbitals. Therefore, shape restoration is not required or beneficial for the exact exchange term (see {{TAG\|NMAXFOCKAE}} and {{TAG\|LMAXFOCKAE}}).
	== Related tags and articles ==		== Related tags and articles ==
	{{TAG\|LRPAFORCE}}		{{TAG\|LRPAFORCE}}

Kresse: Somewhat more pedagogical description.

2025-07-04T12:03:31Z

Somewhat more pedagogical description.

← Older revision		Revision as of 12:03, 4 July 2025
Line 2:		Line 2:
	{{TAGDEF\|LFOCKSTD\|[logical]\|.FALSE.}}		{{TAGDEF\|LFOCKSTD\|[logical]\|.FALSE.}}

	Description: {{TAG\|LFOCKSTD}} ~~uses exact one-centre density terms for~~ the exact exchange ~~part of~~ the ~~total energy and RPA forces~~.		Description: {{TAG\|LFOCKSTD}} applies to RPA and GW calculations. It forces VASP to evaluate the exact exchange fully consistent with the standard treatment in HF calculations.
	----		----
	{{NB\|mind\|Avaliable as of 6.5.2.}}		{{NB\|mind\|Avaliable as of 6.5.2.}}
	This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.		This feature is availabe for low-scaling [[ACFDT/RPA_calculations\| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG\|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.

	~~If selected~~, exact ~~one-center terms~~ in the ~~electronic density for~~ the exact exchange (~~EXX) component of~~ RPA total ~~energies and forces are selected~~.		Usually VASP uses shape restoration (see NMAXFOCKAE and LMAXFOCKAE) for the RPA correlation contributions as well as for the evaluation of the exact exchange during RPA/GW calculations. This however results in signficant noise which is particularly pronounced for the exact exchange. To mitigate this issue, LFOCKSTD was introduced: it forces VASP to use the standard HF-treatment for the exact exchange, but continues to use shape restoration for the correlation contributions. This not only reduces the noise in the force, but also leads to an exact exchange energy that is fully compatible wiht the exact exchange contribution in standard HF calculations (that is the energy " HF-free energy FHF" in the RPA calculations is idential to the "free energy TOTEN " for when reading the WAVECAR file and performing a single step total energy calculation ( ALGO = Eigenval; LFHCALC = .TRUE. ; AEXX = 1.0 ; NELM = 1). This means that this restores the agreement of <code>FHF</code> with the result obtained in the [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].
	This restores the agreement of <code>FHF</code> with the result obtained in the [[ACFDT/RPA_calculations#EXX-inline-ref\|step wise computation of the total energy]].

	It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.5.2.		It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.5.2.

Kaltakm: Created page with "{{DISPLAYTITLE:LFOCKSTD}} {{TAGDEF|LFOCKSTD|[logical]|.FALSE.}} Description: {{TAG|LFOCKSTD}} uses exact one-centre density terms for the exact exchange part of the total energy and RPA forces. ---- {{NB|mind|Avaliable as of 6.5.2.}} This feature is availabe for low-scaling ACFDT/random-phase-approximation (RPA) and GW calculations, i.e. {{TAG|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR. If selected, exact one-center terms in the electronic densit..."

2025-05-02T13:00:52Z

Created page with "{{DISPLAYTITLE:LFOCKSTD}} {{TAGDEF|LFOCKSTD|[logical]|.FALSE.}} Description: {{TAG|LFOCKSTD}} uses exact one-centre density terms for the exact exchange part of the total energy and RPA forces. ---- {{NB|mind|Avaliable as of 6.5.2.}} This feature is availabe for low-scaling ACFDT/random-phase-approximation (RPA) and GW calculations, i.e. {{TAG|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR. If selected, exact one-center terms in the electronic densit..."

New page

{{DISPLAYTITLE:LFOCKSTD}}
{{TAGDEF|LFOCKSTD|[logical]|.FALSE.}}

Description: {{TAG|LFOCKSTD}} uses exact one-centre density terms for the exact exchange part of the total energy and RPA forces.
----
{{NB|mind|Avaliable as of 6.5.2.}}
This feature is availabe for low-scaling [[ACFDT/RPA_calculations| ACFDT/random-phase-approximation (RPA)]] and [[GW calculations]], i.e. {{TAG|ALGO}}=ACFDTR, RPAR, EVGW0R, GWR.

If selected, exact one-center terms in the electronic density for the exact exchange (EXX) component of RPA total energies and forces are selected.
This restores the agreement of <code>FHF</code> with the result obtained in the [[ACFDT/RPA_calculations#EXX-inline-ref|step wise computation of the total energy]].

It is strongly recommended to activate LFOCKSTD for all GW and RPA calculations starting from version 6.5.2.

In earlier versions, one-center density contributions of EXX can be treated only with shape and electrostatic multipole reconstruction using {{TAG|LMAXFOCKAE}}.
== Related tags and articles ==
{{TAG|LRPAFORCE}}
----

[[Category:INCAR tag]][[Category:Many-body perturbation theory]][[Category:GW]] [[Category:ACFDT]][[Category:Low-scaling GW and RPA]]