LSPECTRALGW - Revision history

Huebsch at 10:12, 19 July 2022

2022-07-19T10:12:06Z

← Older revision		Revision as of 10:12, 19 July 2022
Line 22:		Line 22:
	----		----

	[[Category:INCAR tag]][[Category:Many-~~Body Perturbation Theory~~]] [[Category:GW]]		[[Category:INCAR tag]][[Category:Many-body perturbation theory]][[Category:GW]]

Karsai: /* Related Tags and Sections */

2022-04-08T14:42:45Z

Related Tags and Sections

← Older revision		Revision as of 14:42, 8 April 2022
Line 16:		Line 16:


	== Related ~~Tags~~ and ~~Sections~~ ==		== Related tags and articles ==
	{{TAG\|LSPECTRAL}}		{{TAG\|LSPECTRAL}}

Line 22:		Line 22:
	----		----

	[[Category:INCAR]][[Category:Many-Body Perturbation Theory]] [[Category:GW]]		[[Category:INCAR tag]][[Category:Many-Body Perturbation Theory]] [[Category:GW]]

Karsai at 14:59, 11 March 2019

2019-03-11T14:59:13Z

← Older revision		Revision as of 14:59, 11 March 2019
Line 21:		Line 21:
	{{sc\|LSPECTRALGW\|Examples\|Examples that use this tag}}		{{sc\|LSPECTRALGW\|Examples\|Examples that use this tag}}
	----		----
	~~[[The_VASP_Manual\|Contents]]~~

	[[Category:INCAR]] [[Category:GW]]		[[Category:INCAR]][[Category:Many-Body Perturbation Theory]] [[Category:GW]]

Kresse at 16:12, 15 September 2017

2017-09-15T16:12:42Z

← Older revision		Revision as of 16:12, 15 September 2017
Line 8:		Line 8:
	Generally, {{TAG\|LSPECTRALGW}} affects the compute time very little. QP energies also hardly		Generally, {{TAG\|LSPECTRALGW}} affects the compute time very little. QP energies also hardly
	change when {{TAG\|LSPECTRALGW}} is modified.		change when {{TAG\|LSPECTRALGW}} is modified.
	However, {{TAG\|LSPECTRALGW}} = .TRUE. is usually is slightly more robust,		However, {{TAG\|LSPECTRALGW}} = .TRUE. is usually slightly more robust,
	and should be selected for molecules and other systems with flat bands.		and should be selected for molecules and other systems with flat dispersion-less bands.
	One the other hand, {{TAG\|LSPECTRALGW}} = .TRUE. seems to converge slightly slower,		One the other hand, {{TAG\|LSPECTRALGW}} = .TRUE. seems to converge slightly slower,
	as the complex shift {{TAG\|CSHIFT}} is decreased. Set this flag, if the QP energies		as the complex shift {{TAG\|CSHIFT}} is decreased. Set this flag, if the QP energies
	show erratic behavior, for instance, if QP energies or Z-factors are not in the expected		show erratic behavior, for instance, if QP energies or Z-factors are not in the expected
	range of values.		range of values (0.5<Z<0.9).

Karsai at 10:33, 20 March 2017

2017-03-20T10:33:22Z

← Older revision		Revision as of 10:33, 20 March 2017
Line 19:		Line 19:
	{{TAG\|LSPECTRAL}}		{{TAG\|LSPECTRAL}}

	~~== Example Calculations using~~ this ~~Tag ==~~		{{sc\|LSPECTRALGW\|Examples\|Examples that use this tag}}
	----		----
	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:INCAR]] [[Category:GW]]		[[Category:INCAR]] [[Category:GW]]

Kresse at 18:18, 13 March 2017

2017-03-13T18:18:56Z

← Older revision		Revision as of 18:18, 13 March 2017
Line 1:		Line 1:
	{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}		{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.\|.FALSE.}}
	~~{{DEF\|LSPECTRALGW~~\|.FALSE.\|}}

	Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.		Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.

Kresse at 18:18, 13 March 2017

2017-03-13T18:18:15Z

← Older revision		Revision as of 18:18, 13 March 2017
Line 1:		Line 1:
	{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}		{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}
	{{DEF\|LSPECTRALGW\|.FALSE.}}		{{DEF\|LSPECTRALGW\|.FALSE.\|}}

	Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.		Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.

Kresse at 18:15, 13 March 2017

2017-03-13T18:15:58Z

← Older revision		Revision as of 18:15, 13 March 2017
Line 12:		Line 12:
	and should be selected for molecules and other systems with flat bands.		and should be selected for molecules and other systems with flat bands.
	One the other hand, {{TAG\|LSPECTRALGW}} = .TRUE. seems to converge slightly slower,		One the other hand, {{TAG\|LSPECTRALGW}} = .TRUE. seems to converge slightly slower,
	as the complex shift {{TAG\|CSHIFT}} is decreased.		as the complex shift {{TAG\|CSHIFT}} is decreased. Set this flag, if the QP energies
			show erratic behavior, for instance, if QP energies or Z-factors are not in the expected
			range of values.

Kresse at 18:13, 13 March 2017

2017-03-13T18:13:13Z

← Older revision		Revision as of 18:13, 13 March 2017
Line 1:		Line 1:
	{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}		{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}
	{{DEF\|LSPECTRALGW\|.~~TRUE~~.~~\|if {{TAG\|NOMEGA}}>2~~}}		{{DEF\|LSPECTRALGW\|.FALSE.}}

	Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method.		Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.
	----		----

	If {{TAG\|LSPECTRALGW}} = .TRUE. is set, the imaginary part of the ~~independent particle polarizability~~ <math>\~~chi_{\mathbf{q}}^0~~ (~~\mathbf{G}, \mathbf{G}',~~ \omega)</math> is calculated ~~first, and afterwards~~ the ~~full independent particle polarizability is determined using a Kramers-Kronig~~ (~~or Hilbert~~) ~~transform~~. ~~This reduces~~ the ~~computational work load by almost a factor~~ {{TAG\|~~NOMEGA~~}}/2. ~~The downside of the coin~~ is ~~that the response function must~~ be ~~kept in memory~~ for ~~all considered frequencies~~, ~~which can cause excessive memory requirements~~. ~~VASP therefore distributes~~ the ~~dielectric functions among the available compute nodes~~.		If {{TAG\|LSPECTRALGW}} = .TRUE. is set, the imaginary part of the self-energy <math>\Sigma(\omega)= G W</math> is calculated from the imaginary part of screened potential <math>W(\omega)</math> by shifting the poles of
			<math>W </math> by <math> \pm \epsilon </math>, where <math> \epsilon </math> are the poles of the Green's function <math> G</math>.
			Generally, {{TAG\|LSPECTRALGW}} affects the compute time very little. QP energies also hardly
			change when {{TAG\|LSPECTRALGW}} is modified.
			However, {{TAG\|LSPECTRALGW}} = .TRUE. is usually is slightly more robust,
			and should be selected for molecules and other systems with flat bands.
			One the other hand, {{TAG\|LSPECTRALGW}} = .TRUE. seems to converge slightly slower,
			as the complex shift {{TAG\|CSHIFT}} is decreased.

	~~A similar trick is used when the QP-shifts are calculated. In general it is strongly recommended to set {{TAG\|LSPECTRALGW}} = .TRUE., except if memory requirements are too excessive.~~

	== Related Tags and Sections ==		== Related Tags and Sections ==

Kresse: /* Related Tags and Sections */

2017-03-13T17:53:26Z

Related Tags and Sections

← Older revision		Revision as of 17:53, 13 March 2017
Line 10:		Line 10:

	== Related Tags and Sections ==		== Related Tags and Sections ==
	{{TAG\|~~NOMEGA~~}}		{{TAG\|LSPECTRAL}}

	== Example Calculations using this Tag ==		== Example Calculations using this Tag ==

← Older revision		Revision as of 18:18, 13 March 2017
Line 1:		Line 1:
	{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}		{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.\|.FALSE.}}
	~~{{DEF\|LSPECTRALGW~~\|.FALSE.\|}}

	Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.		Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.

← Older revision		Revision as of 18:18, 13 March 2017
Line 1:		Line 1:
	{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}		{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}
	{{DEF\|LSPECTRALGW\|.FALSE.}}		{{DEF\|LSPECTRALGW\|.FALSE.\|}}

	Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.		Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.

← Older revision		Revision as of 18:13, 13 March 2017
Line 1:		Line 1:
	{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}		{{TAGDEF\|LSPECTRALGW\|.FALSE. {{!}} .TRUE.}}
	{{DEF\|LSPECTRALGW\|.~~TRUE~~.~~\|if {{TAG\|NOMEGA}}>2~~}}		{{DEF\|LSPECTRALGW\|.FALSE.}}

	Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method.		Description: {{TAG\|LSPECTRALGW}} specifies to use the spectral method for calculating the self-energy.
	----		----

	If {{TAG\|LSPECTRALGW}} = .TRUE. is set, the imaginary part of the ~~independent particle polarizability~~ <math>\~~chi_{\mathbf{q}}^0~~ (~~\mathbf{G}, \mathbf{G}',~~ \omega)</math> is calculated ~~first, and afterwards~~ the ~~full independent particle polarizability is determined using a Kramers-Kronig~~ (~~or Hilbert~~) ~~transform~~. ~~This reduces~~ the ~~computational work load by almost a factor~~ {{TAG\|~~NOMEGA~~}}/2. ~~The downside of the coin~~ is ~~that the response function must~~ be ~~kept in memory~~ for ~~all considered frequencies~~, ~~which can cause excessive memory requirements~~. ~~VASP therefore distributes~~ the ~~dielectric functions among the available compute nodes~~.		If {{TAG\|LSPECTRALGW}} = .TRUE. is set, the imaginary part of the self-energy <math>\Sigma(\omega)= G W</math> is calculated from the imaginary part of screened potential <math>W(\omega)</math> by shifting the poles of
			<math>W </math> by <math> \pm \epsilon </math>, where <math> \epsilon </math> are the poles of the Green's function <math> G</math>.
			Generally, {{TAG\|LSPECTRALGW}} affects the compute time very little. QP energies also hardly
			change when {{TAG\|LSPECTRALGW}} is modified.
			However, {{TAG\|LSPECTRALGW}} = .TRUE. is usually is slightly more robust,
			and should be selected for molecules and other systems with flat bands.
			One the other hand, {{TAG\|LSPECTRALGW}} = .TRUE. seems to converge slightly slower,
			as the complex shift {{TAG\|CSHIFT}} is decreased.

	~~A similar trick is used when the QP-shifts are calculated. In general it is strongly recommended to set {{TAG\|LSPECTRALGW}} = .TRUE., except if memory requirements are too excessive.~~

	== Related Tags and Sections ==		== Related Tags and Sections ==