Band decomposed charge densities - Revision history

Wolloch: Redirected page to Band-decomposed charge densities

2024-02-09T16:47:06Z

Redirected page to Band-decomposed charge densities

← Older revision		Revision as of 16:47, 9 February 2024
Line 1:		Line 1:
	VASP can calculate the partial (band decomposed) charge density according to parameters specified in the {{TAG\|INCAR}} file. It must be noted, that the densities calculated by VASP (including the band decomposed charge density) are always symmetrized using the space group and point group symmetry determined by VASP. In some cases (calculation of charge from selected k-~~points) this can lead to undesired results for the band decomposed charge density. In this case, the symmetry needs to be switched off for the ground state and successive band~~ decomposed ~~charge density calculations.~~		#REDIRECT [[Band-decomposed charge densities]]

	Mind that the partial charge density can be calculated only if a preconverged {{TAG\|WAVECAR}} file exists, VASP enters the evaluation routine very quickly and stops immediately after evaluating the partial charge densities~~. This implementation was chosen to allow a fast (almost interactive) recalculation of the charge density for particular bands and k-points.~~

	~~The following parameters control the behaviour of VASP:~~

	*{{TAG\|LPARD}}: Evaluate partial (band and/or k-point) decomposed charge densities. We want to stress again, that the orbitals read from {{TAG\|WAVECAR}} must be converged in a separate prior run. If only {{TAG\|LPARD}} is set (and none of the tags discussed below), the total charge density is evaluated from the orbitals and written to {{TAG\|CHGCAR}}.

	~~There are several ways how to specify for which bands the charge density is evaluated: In general the input lines with {{TAG\|IBAND}}, {{TAG\|EINT}} and {{TAG\|NBMOD}} control this aspect of the routine.~~

	*{{TAG\|IBAND}}: Calculate the partial charge density for all bands specified in the array {{TAG\|IBAND}}. If {{TAG\|IBAND}} is specified in the {{TAG\|INCAR}} file and {{TAG\|NBMOD}} is not given, {{TAG\|NBMOD}} is set automatically to the size of the array. If {{TAG\|IBAND}} is for instance

	~~IBAND = 20 21 22 23~~

	~~the charge density will be calculated for bands 20 to 23.~~

	*{{TAG\|EINT}}: Specifies the energy range of the bands that are used for the evaluation of the partial charge density. Two real values should be given, if only one value is specified, the second one is set to <math>\epsilon_{f}</math>. If {{TAG\|EINT}} is given and {{TAG\|NBMOD}} is not specified, {{TAG\|NBMOD}} is set automatically to -2.

	*{{TAG\|NBMOD}}: This integer variable can take the following values

	>0: Number of values in the array {{TAG\|IBAND}}. If {{TAG\|IBAND}} is specified, {{TAG\|NBMOD}} is set automatically to the correct value (in that case {{TAG\|NBMOD}} should not be set manually in the {{TAG\|INCAR}} file)

	~~0: Take all bands to calculate the charge density, even unoccupied bands are taken into account.~~

	~~-1: Calculate the total charge density as usual. This is the default value if nothing else is given.~~

	~~-2: Calculate the partial charge density for electrons with the eigenvalues in the range specified by {{TAG\|EINT}}.~~

	~~-3: The same as before, but the energy range is given vs. the Fermi energy.~~

	*{{TAG\|KPUSE}}: Specifies which k-points are used in the evaluation of the partial DOS. {{TAG\|KPUSE}} is an array of integer values.

	~~KPUSE= 1 2 3 4~~

	~~means that the charge density is evaluated and summed for the first four k-points. Be careful: VASP changes the k-point weights if {{TAG\|KPUSE}} is specified.~~

	{{TAG\|LSEPB}}: Specifies whether the charge density is calculated for every band separately and written to a file {{TAG\|PARCHG}}.nb.* ({{TAG\|LSEPB}}=''.TRUE.'') or whether charge density is merged for all selected bands and written to the file {{TAG\|PARCHG}}.ALLB.* or {{TAG\|PARCHG}}. Default is {{TAG\|LSEPB}}=''.FALSE.''.

	{{TAG\|LSEPK}}: Specifies whether the charge density of every k-point is write to the files {{TAG\|PARCHG}}.*.nk ({{TAG\|LSEPK}}=''.TRUE.'') or whether it is merged ({{TAG\|LSEPK}}=''.FALSE.'') to a single file. If the merged file is written, then the weight of each k-point is determined from the {{TAG\|KPOINTS}} file, otherwise the kpoints weights of one are chosen.

	Note on spin polarized calculations: for spin polarized calculations, the PARCHG and CHGCAR file hold the total density and the magnetization density. For instance, if the 4th band is selected ({{TAG\|IBAND}}=4) the first data set in the PARCHG file corresponds to the summed density of the 4th spin up and 4th spin down orbital, whereas the second data set holds the difference between the 4th spin-up and 4th spin-down orbital (magnetization density). Hence, to obtain the charge density corresponding to a specific orbital of a specific spin channel some post processing of the {{TAG\|PARCHG}} file might be required (building differences or sums). A simple workaround is to use {{TAG\|EINT}} and specify sufficient digits to select only one orbital from either the spin up or spin down channel.

	~~== Related Tags and Sections ==~~
	~~{{TAG\|LPARD}},~~
	~~{{TAG\|IBAND}},~~
	~~{{TAG\|EINT}},~~
	~~{{TAG\|NBMOD}},~~
	~~{{TAG\|KPUSE}},~~
	~~{{TAG\|LSEPB}}~~
	~~{{TAG\|LSEPK}}~~

	~~{{sc\|Band decomposed charge densities\|Examples\|Examples that use this tag}}~~
	~~----~~

	~~[[Category:Electronic minimization]][[Category:Charge density]][[Category:Howto~~]]

Huebsch at 10:46, 6 April 2022

2022-04-06T10:46:24Z

← Older revision		Revision as of 10:46, 6 April 2022
Line 53:		Line 53:
	----		----

	[[Category:Electronic ~~Minimization~~]][[Category:Charge ~~Density~~]][[Category:Howto]]		[[Category:Electronic minimization]][[Category:Charge density]][[Category:Howto]]

Kresse at 07:12, 18 October 2021

2021-10-18T07:12:13Z

← Older revision		Revision as of 07:12, 18 October 2021
Line 39:		Line 39:
	{{TAG\|LSEPK}}: Specifies whether the charge density of every k-point is write to the files {{TAG\|PARCHG}}.*.nk ({{TAG\|LSEPK}}=''.TRUE.'') or whether it is merged ({{TAG\|LSEPK}}=''.FALSE.'') to a single file. If the merged file is written, then the weight of each k-point is determined from the {{TAG\|KPOINTS}} file, otherwise the kpoints weights of one are chosen.		{{TAG\|LSEPK}}: Specifies whether the charge density of every k-point is write to the files {{TAG\|PARCHG}}.*.nk ({{TAG\|LSEPK}}=''.TRUE.'') or whether it is merged ({{TAG\|LSEPK}}=''.FALSE.'') to a single file. If the merged file is written, then the weight of each k-point is determined from the {{TAG\|KPOINTS}} file, otherwise the kpoints weights of one are chosen.

	Note on spin polarized calculations: for spin polarized calculations, the PARCHG and CHGCAR file hold the total density and the magnetization density. For instance, if the 4th band is selected (IBAND=4) the first data set in the PARCHG file corresponds to the summed density of the 4th spin up and 4th spin down orbital, whereas the second data set holds the difference between the 4th spin-up and 4th spin-down orbital (magnetization density). Hence, to obtain the charge density corresponding to a specific orbital of a specific spin channel some post processing of the PARCHG file might be required (building differences or sums). A simple workaround is to use EINT and specify sufficient digits to select only one orbital from either the spin up or spin down channel.		Note on spin polarized calculations: for spin polarized calculations, the PARCHG and CHGCAR file hold the total density and the magnetization density. For instance, if the 4th band is selected ({{TAG\|IBAND}}=4) the first data set in the PARCHG file corresponds to the summed density of the 4th spin up and 4th spin down orbital, whereas the second data set holds the difference between the 4th spin-up and 4th spin-down orbital (magnetization density). Hence, to obtain the charge density corresponding to a specific orbital of a specific spin channel some post processing of the {{TAG\|PARCHG}} file might be required (building differences or sums). A simple workaround is to use {{TAG\|EINT}} and specify sufficient digits to select only one orbital from either the spin up or spin down channel.

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

Kresse: comment on spin polarized calculations added

2021-10-18T07:11:02Z

comment on spin polarized calculations added

← Older revision		Revision as of 07:11, 18 October 2021
Line 38:		Line 38:

	{{TAG\|LSEPK}}: Specifies whether the charge density of every k-point is write to the files {{TAG\|PARCHG}}.*.nk ({{TAG\|LSEPK}}=''.TRUE.'') or whether it is merged ({{TAG\|LSEPK}}=''.FALSE.'') to a single file. If the merged file is written, then the weight of each k-point is determined from the {{TAG\|KPOINTS}} file, otherwise the kpoints weights of one are chosen.		{{TAG\|LSEPK}}: Specifies whether the charge density of every k-point is write to the files {{TAG\|PARCHG}}.*.nk ({{TAG\|LSEPK}}=''.TRUE.'') or whether it is merged ({{TAG\|LSEPK}}=''.FALSE.'') to a single file. If the merged file is written, then the weight of each k-point is determined from the {{TAG\|KPOINTS}} file, otherwise the kpoints weights of one are chosen.

			Note on spin polarized calculations: for spin polarized calculations, the PARCHG and CHGCAR file hold the total density and the magnetization density. For instance, if the 4th band is selected (IBAND=4) the first data set in the PARCHG file corresponds to the summed density of the 4th spin up and 4th spin down orbital, whereas the second data set holds the difference between the 4th spin-up and 4th spin-down orbital (magnetization density). Hence, to obtain the charge density corresponding to a specific orbital of a specific spin channel some post processing of the PARCHG file might be required (building differences or sums). A simple workaround is to use EINT and specify sufficient digits to select only one orbital from either the spin up or spin down channel.

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

Karsai at 13:59, 15 March 2019

2019-03-15T13:59:12Z

← Older revision		Revision as of 13:59, 15 March 2019
Line 50:		Line 50:
	{{sc\|Band decomposed charge densities\|Examples\|Examples that use this tag}}		{{sc\|Band decomposed charge densities\|Examples\|Examples that use this tag}}
	----		----
	~~[[The_VASP_Manual\|Contents]]~~

	[[Category:Electronic Minimization]][[Category:Charge Density]][[Category:Howto]]		[[Category:Electronic Minimization]][[Category:Charge Density]][[Category:Howto]]

Karsai: /* Related Tags and Sections */

2019-03-07T10:01:39Z

Related Tags and Sections

← Older revision		Revision as of 10:01, 7 March 2019
Line 52:		Line 52:
	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:~~Eletronic~~ Minimization]][[Category:Charge Density]][[Category:Howto]]		[[Category:Electronic Minimization]][[Category:Charge Density]][[Category:Howto]]

Karsai at 10:01, 7 March 2019

2019-03-07T10:01:24Z

← Older revision		Revision as of 10:01, 7 March 2019
Line 52:		Line 52:
	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:Charge Density]][[Category:Howto]]		[[Category:Eletronic Minimization]][[Category:Charge Density]][[Category:Howto]]

Karsai at 17:30, 25 February 2019

2019-02-25T17:30:16Z

← Older revision		Revision as of 17:30, 25 February 2019
Line 52:		Line 52:
	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:Charge Density]]		[[Category:Charge Density]][[Category:Howto]]

Karsai at 17:28, 25 February 2019

2019-02-25T17:28:56Z

← Older revision		Revision as of 17:28, 25 February 2019
Line 52:		Line 52:
	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	~~[[Category:INCAR]]~~[[Category:Charge Density]]		[[Category:Charge Density]]

Karsai at 17:25, 25 February 2019

2019-02-25T17:25:53Z

← Older revision		Revision as of 17:25, 25 February 2019
Line 52:		Line 52:
	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:INCAR]]		[[Category:INCAR]][[Category:Charge Density]]

← Older revision		Revision as of 16:47, 9 February 2024
Line 1:		Line 1:
	VASP can calculate the partial (band decomposed) charge density according to parameters specified in the {{TAG\|INCAR}} file. It must be noted, that the densities calculated by VASP (including the band decomposed charge density) are always symmetrized using the space group and point group symmetry determined by VASP. In some cases (calculation of charge from selected k-~~points) this can lead to undesired results for the band decomposed charge density. In this case, the symmetry needs to be switched off for the ground state and successive band~~ decomposed ~~charge density calculations.~~		#REDIRECT [[Band-decomposed charge densities]]

	Mind that the partial charge density can be calculated only if a preconverged {{TAG\|WAVECAR}} file exists, VASP enters the evaluation routine very quickly and stops immediately after evaluating the partial charge densities~~. This implementation was chosen to allow a fast (almost interactive) recalculation of the charge density for particular bands and k-points.~~

	~~The following parameters control the behaviour of VASP:~~

	*{{TAG\|LPARD}}: Evaluate partial (band and/or k-point) decomposed charge densities. We want to stress again, that the orbitals read from {{TAG\|WAVECAR}} must be converged in a separate prior run. If only {{TAG\|LPARD}} is set (and none of the tags discussed below), the total charge density is evaluated from the orbitals and written to {{TAG\|CHGCAR}}.

	~~There are several ways how to specify for which bands the charge density is evaluated: In general the input lines with {{TAG\|IBAND}}, {{TAG\|EINT}} and {{TAG\|NBMOD}} control this aspect of the routine.~~

	*{{TAG\|IBAND}}: Calculate the partial charge density for all bands specified in the array {{TAG\|IBAND}}. If {{TAG\|IBAND}} is specified in the {{TAG\|INCAR}} file and {{TAG\|NBMOD}} is not given, {{TAG\|NBMOD}} is set automatically to the size of the array. If {{TAG\|IBAND}} is for instance

	~~IBAND = 20 21 22 23~~

	~~the charge density will be calculated for bands 20 to 23.~~

	*{{TAG\|EINT}}: Specifies the energy range of the bands that are used for the evaluation of the partial charge density. Two real values should be given, if only one value is specified, the second one is set to <math>\epsilon_{f}</math>. If {{TAG\|EINT}} is given and {{TAG\|NBMOD}} is not specified, {{TAG\|NBMOD}} is set automatically to -2.

	*{{TAG\|NBMOD}}: This integer variable can take the following values

	>0: Number of values in the array {{TAG\|IBAND}}. If {{TAG\|IBAND}} is specified, {{TAG\|NBMOD}} is set automatically to the correct value (in that case {{TAG\|NBMOD}} should not be set manually in the {{TAG\|INCAR}} file)

	~~0: Take all bands to calculate the charge density, even unoccupied bands are taken into account.~~

	~~-1: Calculate the total charge density as usual. This is the default value if nothing else is given.~~

	~~-2: Calculate the partial charge density for electrons with the eigenvalues in the range specified by {{TAG\|EINT}}.~~

	~~-3: The same as before, but the energy range is given vs. the Fermi energy.~~

	*{{TAG\|KPUSE}}: Specifies which k-points are used in the evaluation of the partial DOS. {{TAG\|KPUSE}} is an array of integer values.

	~~KPUSE= 1 2 3 4~~

	~~means that the charge density is evaluated and summed for the first four k-points. Be careful: VASP changes the k-point weights if {{TAG\|KPUSE}} is specified.~~

	{{TAG\|LSEPB}}: Specifies whether the charge density is calculated for every band separately and written to a file {{TAG\|PARCHG}}.nb.* ({{TAG\|LSEPB}}=''.TRUE.'') or whether charge density is merged for all selected bands and written to the file {{TAG\|PARCHG}}.ALLB.* or {{TAG\|PARCHG}}. Default is {{TAG\|LSEPB}}=''.FALSE.''.

	{{TAG\|LSEPK}}: Specifies whether the charge density of every k-point is write to the files {{TAG\|PARCHG}}.*.nk ({{TAG\|LSEPK}}=''.TRUE.'') or whether it is merged ({{TAG\|LSEPK}}=''.FALSE.'') to a single file. If the merged file is written, then the weight of each k-point is determined from the {{TAG\|KPOINTS}} file, otherwise the kpoints weights of one are chosen.

	Note on spin polarized calculations: for spin polarized calculations, the PARCHG and CHGCAR file hold the total density and the magnetization density. For instance, if the 4th band is selected ({{TAG\|IBAND}}=4) the first data set in the PARCHG file corresponds to the summed density of the 4th spin up and 4th spin down orbital, whereas the second data set holds the difference between the 4th spin-up and 4th spin-down orbital (magnetization density). Hence, to obtain the charge density corresponding to a specific orbital of a specific spin channel some post processing of the {{TAG\|PARCHG}} file might be required (building differences or sums). A simple workaround is to use {{TAG\|EINT}} and specify sufficient digits to select only one orbital from either the spin up or spin down channel.

	~~== Related Tags and Sections ==~~
	~~{{TAG\|LPARD}},~~
	~~{{TAG\|IBAND}},~~
	~~{{TAG\|EINT}},~~
	~~{{TAG\|NBMOD}},~~
	~~{{TAG\|KPUSE}},~~
	~~{{TAG\|LSEPB}}~~
	~~{{TAG\|LSEPK}}~~

	~~{{sc\|Band decomposed charge densities\|Examples\|Examples that use this tag}}~~
	~~----~~

	~~[[Category:Electronic minimization]][[Category:Charge density]][[Category:Howto~~]]