ADDGRID - Revision history

Csheldon at 11:33, 6 May 2026

2026-05-06T11:33:30Z

← Older revision		Revision as of 11:33, 6 May 2026
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	----		----
	When {{TAG\|ADDGRID}}=.TRUE. VASP uses an additional support grid for the evaluation of the augmentation charges. This grid contains 8 times more points than the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). Whenever terms involving augmentation charges are evaluated, this additional grid is used. For instance: The augmentation charge is evaluated first in real space on this additional grid, FFT-transformed to reciprocal space, and then added to the total charge density on the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). The additional grid often helps to reduce the noise in the forces. In some cases, it even allows to perform calculations with {{TAG\|NGXF}}{{=}}{{TAG\|NGX}}.		When {{TAG\|ADDGRID}}=.TRUE. VASP uses an additional support grid for the evaluation of the augmentation charges. This grid contains 8 times more points than the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). Whenever terms involving augmentation charges are evaluated, this additional grid is used. For instance: The augmentation charge is evaluated first in real space on this additional grid, FFT-transformed to reciprocal space, and then added to the total charge density on the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). The additional grid often helps to reduce the noise in the forces. In some cases, it even allows to perform calculations with {{TAG\|NGXF}}{{=}}{{TAG\|NGX}}.
	{{NB\|important\|If there is any contribution in the density or potential at the highest Fourier component <math>G</math> of		{{NB\|important\|If there is any contribution in the density or potential at the highest Fourier component <math>G</math> of the conventional fine grid (given by {{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}), then Fourier interpolation to twice the grid density leads to oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{i G_{cut} r}</math>. In real space, the charge density or potential will therefore alternate between positive and negative values on the ultra-fine grid, in particular, in regions where the density or potential are small. The terminus techniques is "termination wiggles". Although this is a somewhat oversimplified presentation, it is fairly straightforward to derive more rigorous results in 1D. The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations <math>e^{i G_{cut} r}</math> in the interpolated potential (where <math> G_{cut}</math> corresponds to the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space. Therefore, we recommend performing careful tests, on whether {{TAG\|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!}}
	the conventional fine grid (given by {{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}), then Fourier interpolation to twice the grid density leads to
	oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{i G_{cut} r}</math>.
	In real space, the charge density or potential will therefore alternate between positive and negative
	values on the ultra-fine grid, in particular, in regions where the density or potential are small.
	The terminus techniques is "termination wiggles".
	Although this is a somewhat oversimplified presentation, it is fairly straightforward to derive more rigorous results in 1D.
	The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations <math>e^{i G_{cut} r}</math> in the interpolated potential (where <math> G_{cut}</math> corresponds to
	the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space.
	Therefore, we recommend performing careful tests, on whether {{TAG\|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!}}

	== Related tags and articles ==		== Related tags and articles ==

Csheldon at 11:32, 6 May 2026

2026-05-06T11:32:13Z

← Older revision		Revision as of 11:32, 6 May 2026
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	Description: {{TAG\|ADDGRID}} determines whether an additional support grid is used for the evaluation of the augmentation charges.		Description: {{TAG\|ADDGRID}} determines whether an additional support grid is used for the evaluation of the augmentation charges.
	----		----
	When {{TAG\|ADDGRID}}=.TRUE. VASP uses an additional support grid for the evaluation of the augmentation charges. This grid contains 8 times more points than the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). Whenever terms involving augmentation charges are evaluated, this additional grid is used. For instance: The augmentation charge is evaluated first in real space on this additional grid, FFT-transformed to reciprocal space, and then added to the total charge density on the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). The additional grid often helps to reduce the noise in the forces. In some cases, it even allows to perform calculations with {{TAG\|NGXF}}={{TAG\|NGX}}.		When {{TAG\|ADDGRID}}=.TRUE. VASP uses an additional support grid for the evaluation of the augmentation charges. This grid contains 8 times more points than the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). Whenever terms involving augmentation charges are evaluated, this additional grid is used. For instance: The augmentation charge is evaluated first in real space on this additional grid, FFT-transformed to reciprocal space, and then added to the total charge density on the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). The additional grid often helps to reduce the noise in the forces. In some cases, it even allows to perform calculations with {{TAG\|NGXF}}{{=}}{{TAG\|NGX}}.
			{{NB\|important\|If there is any contribution in the density or potential at the highest Fourier component <math>G</math> of
	~~Caveat:~~
	If there is any contribution in the density or potential at the highest Fourier component <math>G</math> of
	the conventional fine grid (given by {{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}), then Fourier interpolation to twice the grid density leads to		the conventional fine grid (given by {{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}), then Fourier interpolation to twice the grid density leads to
	oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{i G_{cut} r}</math>.		oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{i G_{cut} r}</math>.
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	The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations <math>e^{i G_{cut} r}</math> in the interpolated potential (where <math> G_{cut}</math> corresponds to		The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations <math>e^{i G_{cut} r}</math> in the interpolated potential (where <math> G_{cut}</math> corresponds to
	the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space.		the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space.
	Therefore, we recommend performing careful tests, on whether {{TAG\|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!		Therefore, we recommend performing careful tests, on whether {{TAG\|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!}}

	== Related tags and articles ==		== Related tags and articles ==

Huebsch at 09:24, 17 October 2024

2024-10-17T09:24:43Z

← Older revision		Revision as of 09:24, 17 October 2024
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	{{sc\|ADDGRID\|Examples\|Examples that use this tag}}		{{sc\|ADDGRID\|Examples\|Examples that use this tag}}
	~~----~~
	[[Category:INCAR tag]][[Category:~~Electronic minimization]][[Category:PAW~~]]		[[Category:INCAR tag]][[Category:Projector-augmented-wave method]]

Ftran at 12:12, 18 October 2023

2023-10-18T12:12:48Z

← Older revision		Revision as of 12:12, 18 October 2023
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	{{sc\|ADDGRID\|Examples\|Examples that use this tag}}		{{sc\|ADDGRID\|Examples\|Examples that use this tag}}
	----		----
	~~[[The_VASP_Manual\|Contents]]~~

	[[Category:INCAR tag]][[Category:Electronic minimization]][[Category:PAW]]		[[Category:INCAR tag]][[Category:Electronic minimization]][[Category:PAW]]

Ftran at 08:11, 13 October 2023

2023-10-13T08:11:53Z

@@ Line 16: / Line 16: @@
 the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space.
 Therefore, we recommend performing careful tests, on whether {{TAG|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!
 {{sc|ADDGRID|Examples|Examples that use this tag}}

Karsai at 14:05, 8 April 2022

2022-04-08T14:05:26Z

← Older revision		Revision as of 14:05, 8 April 2022
Line 21:		Line 21:
	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:INCAR]][[Category:Electronic minimization]][[Category:PAW]]		[[Category:INCAR tag]][[Category:Electronic minimization]][[Category:PAW]]

Huebsch at 09:57, 6 April 2022

2022-04-06T09:57:45Z

Miranda.henrique at 08:02, 5 February 2021

2021-02-05T08:02:21Z

← Older revision		Revision as of 08:02, 5 February 2021
Line 1:		Line 1:
	<{{TAGDEF\|ADDGRID\|.TRUE. {{!}} .FALSE. \|.FALSE.}}		{{TAGDEF\|ADDGRID\|.TRUE. {{!}} .FALSE. \|.FALSE.}}

	Description: {{TAG\|ADDGRID}} determines whether an additional support grid is used for the evaluation of the augmentation charges.		Description: {{TAG\|ADDGRID}} determines whether an additional support grid is used for the evaluation of the augmentation charges.

Kresse at 07:02, 18 August 2020

2020-08-18T07:02:33Z

← Older revision		Revision as of 07:02, 18 August 2020
Line 8:		Line 8:
	If there is any contribution in the density or potential at the highest Fourier component <math>G</math> of		If there is any contribution in the density or potential at the highest Fourier component <math>G</math> of
	the conventional fine grid (given by {{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}), then Fourier interpolation to twice the grid density leads to		the conventional fine grid (given by {{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}), then Fourier interpolation to twice the grid density leads to
	oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{(i G_{cut} r)}</math>.		oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{i G_{cut} r}</math>.
	In real space, the charge density or potential will therefore alternate between positive and negative		In real space, the charge density or potential will therefore alternate between positive and negative
	values on the ultra-fine grid, in particular, in regions where the density or potential are small.		values on the ultra-fine grid, in particular, in regions where the density or potential are small.

Kresse at 07:02, 18 August 2020

2020-08-18T07:02:04Z

← Older revision		Revision as of 07:02, 18 August 2020
Line 10:		Line 10:
	oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{(i G_{cut} r)}</math>.		oscillations in real space. These oscillations correspond to the largest wave vector <math> G_{cut} </math> i.e. <math>e^{(i G_{cut} r)}</math>.
	In real space, the charge density or potential will therefore alternate between positive and negative		In real space, the charge density or potential will therefore alternate between positive and negative
	values, in particular, in regions where the density or potential is small.		values on the ultra-fine grid, in particular, in regions where the density or potential are small.
	The terminus techniques is "termination wiggles".		The terminus techniques is "termination wiggles".
	Although this is a somewhat over-simplified presentation, it is fairly straightforward to derive more rigorous results in 1D.		Although this is a somewhat over-simplified presentation, it is fairly straightforward to derive more rigorous results in 1D.
	The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations ~~in the interpolated charge density or potential~~ <math>e^{i G_{cut} r}</math> (where <math> G_{cut}</math> corresponds to		The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations <math>e^{i G_{cut} r}</math> in the interpolated potential (where <math> G_{cut}</math> corresponds to
	the largest Fourier components on the fine grid). Therefore, we recommend to perform careful tests, whether {{TAG\|ADDGRID}} works as desired; please do not use		the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space.
	this tag as default in all your calculations!		Therefore, we recommend to perform careful tests, whether {{TAG\|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!


	{{sc\|ADDGRID\|Examples\|Examples that use this tag}}		{{sc\|ADDGRID\|Examples\|Examples that use this tag}}

← Older revision		Revision as of 09:57, 6 April 2022
Line 3:		Line 3:
	Description: {{TAG\|ADDGRID}} determines whether an additional support grid is used for the evaluation of the augmentation charges.		Description: {{TAG\|ADDGRID}} determines whether an additional support grid is used for the evaluation of the augmentation charges.
	----		----
	When {{TAG\|ADDGRID}}=.TRUE. VASP uses an additional support grid for the evaluation of the augmentation charges. This grid contains 8 times more points than the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). Whenever terms involving augmentation charges are evaluated, this additional grid is used. For instance: The augmentation charge is evaluated first in real space on this additional grid, FFT-transformed to reciprocal space and then added to the total charge density on the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). The additional grid often helps to reduce the noise in the forces. In some cases, it even allows to perform calculations with {{TAG\|NGXF}}={{TAG\|NGX}}.		When {{TAG\|ADDGRID}}=.TRUE. VASP uses an additional support grid for the evaluation of the augmentation charges. This grid contains 8 times more points than the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). Whenever terms involving augmentation charges are evaluated, this additional grid is used. For instance: The augmentation charge is evaluated first in real space on this additional grid, FFT-transformed to reciprocal space, and then added to the total charge density on the standard "fine" grid ({{TAG\|NGXF}}×{{TAG\|NGYF}}×{{TAG\|NGZF}}). The additional grid often helps to reduce the noise in the forces. In some cases, it even allows to perform calculations with {{TAG\|NGXF}}={{TAG\|NGX}}.

	Caveat:		Caveat:
Line 12:		Line 12:
	values on the ultra-fine grid, in particular, in regions where the density or potential are small.		values on the ultra-fine grid, in particular, in regions where the density or potential are small.
	The terminus techniques is "termination wiggles".		The terminus techniques is "termination wiggles".
	Although this is a somewhat ~~over-simplified~~ presentation, it is fairly straightforward to derive more rigorous results in 1D.		Although this is a somewhat oversimplified presentation, it is fairly straightforward to derive more rigorous results in 1D.
	The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations <math>e^{i G_{cut} r}</math> in the interpolated potential (where <math> G_{cut}</math> corresponds to		The upshot is that Fourier-interpolation can lead to termination wiggles with oscillations <math>e^{i G_{cut} r}</math> in the interpolated potential (where <math> G_{cut}</math> corresponds to
	the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space.		the largest Fourier components on the fine grid). Fourier smoothing, which is in essence used for the augmentation densities, is generally less problematic, but it can also result in negative density in real space.
	Therefore, we recommend ~~to perform~~ careful tests, whether {{TAG\|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!		Therefore, we recommend performing careful tests, on whether {{TAG\|ADDGRID}} works as desired; please do not use this tag as default in all your calculations!

	{{sc\|ADDGRID\|Examples\|Examples that use this tag}}		{{sc\|ADDGRID\|Examples\|Examples that use this tag}}
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	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:INCAR]][[Category:Electronic ~~Minimization~~]][[Category:PAW]]		[[Category:INCAR]][[Category:Electronic minimization]][[Category:PAW]]