NBANDSO - Revision history

Tal at 09:17, 24 June 2022

2022-06-24T09:17:58Z

← Older revision		Revision as of 09:17, 24 June 2022
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	{{TAGDEF\|NBANDSO\|[integer]}}		{{TAGDEF\|NBANDSO\|[integer]}}
			{{DEF\|NBANDSO\|number of occupied orbitals\|}}
	Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the Casida/[[BSE calculations]] or time propagation ({{TAG\|ALGO}}=TIMEEV.		Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the Casida/[[BSE calculations]] or time propagation ({{TAG\|ALGO}}=TIMEEV.

Huebsch at 12:26, 7 April 2022

2022-04-07T12:26:57Z

← Older revision		Revision as of 12:26, 7 April 2022
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	{{TAGDEF\|NBANDSO\|[integer]}}		{{TAGDEF\|NBANDSO\|[integer]}}

	Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the		Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the Casida/[[BSE calculations]] or time propagation ({{TAG\|ALGO}}=TIMEEV.
	Casida/[[BSE calculations]] or ~~[[timepropagation]]~~

	----		----
	For the ~~timepropagation~~ algorithm increasing {{TAG\|NBANDSO}} only modestly increases the compute time.		For the time-propagation algorithm increasing {{TAG\|NBANDSO}} only modestly increases the compute time.
	For BSE and Casida type calculations, the compute time grows with the third power of the number of included occupied and unoccupied bands		For BSE and Casida-type calculations, the compute time grows with the third power of the number of included occupied and unoccupied bands

	<math> (N_{\mathrm{occ}} N_{\mathrm{virtual}} N_{\mathrm{k}})^{3} </math>		<math> (N_{\mathrm{occ}} N_{\mathrm{virtual}} N_{\mathrm{k}})^{3} </math>
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	<math> (N_{\mathrm{occ}}N_{\mathrm{virtual}} N_{\mathrm{k}})^{2} </math>		<math> (N_{\mathrm{occ}}N_{\mathrm{virtual}} N_{\mathrm{k}})^{2} </math>

	Please be aware that symmetry is not exploited in the BSE code, hence memory requirements can be excessive. To allow for calculations on large systems, the BSE code distributes the BSE matrix among all available cores, and uses ~~scaLAPACK~~ for the diagonalization.		Please be aware that symmetry is not exploited in the BSE code, hence memory requirements can be excessive. To allow for calculations on large systems, the BSE code distributes the BSE matrix among all available cores and uses ScaLAPACK for the diagonalization.

	VASP always uses the orbitals closest to the Fermi-level, and {{TAG\|NBANDSO}} (<math>N_{\mathrm{occ}}</math>) and {{TAG\|NBANDSV}} (<math>N_{\mathrm{virtual}}</math>) determines how many occupied and unoccupied orbitals are included. The defaults are fairly "conservative" and equal the total number of electrons/2 (this usually implies that all occupied ~~state~~ are included). For highly accurate results, {{TAG\|NBANDSV}} often needs to be increased, whereas for large systems one is often forced to reduce both values to much smaller numbers. Sometimes qualitative results for ~~band like~~ Wannier-Mott excitons can be obtained even with a single conduction and valence band.		VASP always uses the orbitals closest to the Fermi-level, and {{TAG\|NBANDSO}} (<math>N_{\mathrm{occ}}</math>) and {{TAG\|NBANDSV}} (<math>N_{\mathrm{virtual}}</math>) determines how many occupied and unoccupied orbitals are included. The defaults are fairly "conservative" and equal the total number of electrons/2 (this usually implies that all occupied states are included). For highly accurate results, {{TAG\|NBANDSV}} often needs to be increased, whereas for large systems one is often forced to reduce both values to much smaller numbers. Sometimes qualitative results for bandlike Wannier-Mott excitons can be obtained even with a single conduction and valence band.

	== Related ~~Tags~~ and ~~Sections~~ ==		== Related tags and articles ==
	{{TAG\|NBANDSV}},		{{TAG\|NBANDSV}},
	[[BSE calculations]],		[[BSE calculations]],
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	----		----

	[[Category:INCAR]] [[Category:Many-~~Body Perturbation Theory~~]][[Category:~~BSE~~]]		[[Category:INCAR tag]][[Category:Many-body perturbation theory]][[Category:Bethe-Salpeter equations]]

Karsai at 15:06, 11 March 2019

2019-03-11T15:06:26Z

← Older revision		Revision as of 15:06, 11 March 2019
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	{{sc\|NBANDSO\|Examples\|Examples that use this tag}}		{{sc\|NBANDSO\|Examples\|Examples that use this tag}}
	----		----

	~~[[The_VASP_Manual\|Contents]]~~

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

Karsai at 14:53, 11 March 2019

2019-03-11T14:53:23Z

← Older revision		Revision as of 14:53, 11 March 2019
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	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

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

Kresse at 13:41, 28 March 2018

2018-03-28T13:41:08Z

← Older revision		Revision as of 13:41, 28 March 2018
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	----		----
	For the timepropagation algorithm increasing NBANDSO only modestly increases the compute time.		For the timepropagation algorithm increasing {{TAG\|NBANDSO}} only modestly increases the compute time.
	For BSE and Casida type calculations, the compute time grows with the third power of the number of included occupied and unoccupied bands		For BSE and Casida type calculations, the compute time grows with the third power of the number of included occupied and unoccupied bands

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	== Related Tags and Sections ==		== Related Tags and Sections ==
	{{TAG\|NBANDSV}}.		{{TAG\|NBANDSV}},
	~~{{TAG\|~~BSE calculations}}		[[BSE calculations]],
			[[Timepropagation]]

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

Kresse at 13:36, 28 March 2018

2018-03-28T13:36:15Z

← Older revision		Revision as of 13:36, 28 March 2018
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	{{TAGDEF\|NBANDSO\|[integer]}}		{{TAGDEF\|NBANDSO\|[integer]}}

	Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the BSE calculations.		Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the
			Casida/[[BSE calculations]] or [[timepropagation]]

	----		----
			For the timepropagation algorithm increasing NBANDSO only modestly increases the compute time.
	~~The~~ compute time ~~for~~ BSE and ~~Cassida~~ type calculations grows with the third power of the number of included occupied and unoccupied bands		For BSE and Casida type calculations, the compute time grows with the third power of the number of included occupied and unoccupied bands

	<math> (N_{\mathrm{occ}} N_{\mathrm{virtual}} N_{\mathrm{k}})^{3} </math>		<math> (N_{\mathrm{occ}} N_{\mathrm{virtual}} N_{\mathrm{k}})^{3} </math>

Karsai at 10:40, 20 March 2017

2017-03-20T10:40:40Z

← Older revision		Revision as of 10:40, 20 March 2017
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	{{TAG\|BSE calculations}}		{{TAG\|BSE calculations}}

	~~== Example Calculations using this Tag ==~~		{{sc\|NBANDSO\|Examples\|Examples that use this tag}}
	{{~~TAG~~\|~~Dielectric properties of Si using BSE}}, {{TAG~~\|~~Model BSE calculation on Si~~}}
	----		----

Karsai at 15:48, 16 March 2017

2017-03-16T15:48:32Z

← Older revision		Revision as of 15:48, 16 March 2017
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	----		----

	The compute time for BSE and Cassida type calculations ~~growswith~~ the third power of the number of included occupied and unoccupied bands		The compute time for BSE and Cassida type calculations grows with the third power of the number of included occupied and unoccupied bands

	<math> (N_{\mathrm{occ}} N_{\mathrm{virtual}} N_{\mathrm{k}})^{3} </math>		<math> (N_{\mathrm{occ}} N_{\mathrm{virtual}} N_{\mathrm{k}})^{3} </math>

Karsai at 11:16, 24 February 2017

2017-02-24T11:16:00Z

← Older revision		Revision as of 11:16, 24 February 2017
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	{{TAG\|BSE calculations}}		{{TAG\|BSE calculations}}

			== Example Calculations using this Tag ==
			{{TAG\|Dielectric properties of Si using BSE}}, {{TAG\|Model BSE calculation on Si}}
	----		----

Karsai at 10:34, 21 January 2017

2017-01-21T10:34:11Z

← Older revision		Revision as of 10:34, 21 January 2017
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	== Related Tags and Sections ==		== Related Tags and Sections ==
	{{TAG\|NBANDSV}}		{{TAG\|NBANDSV}}.
			{{TAG\|BSE calculations}}

	----		----

	[[The_VASP_Manual\|Contents]]		[[The_VASP_Manual\|Contents]]

	[[Category:INCAR]] [[Category:BSE]]		[[Category:INCAR]] [[Category:BSE]]

← Older revision		Revision as of 09:17, 24 June 2022
Line 1:		Line 1:
	{{TAGDEF\|NBANDSO\|[integer]}}		{{TAGDEF\|NBANDSO\|[integer]}}
			{{DEF\|NBANDSO\|number of occupied orbitals\|}}
	Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the Casida/[[BSE calculations]] or time propagation ({{TAG\|ALGO}}=TIMEEV.		Description: {{TAG\|NBANDSO}} determines how many occupied orbitals are included in the Casida/[[BSE calculations]] or time propagation ({{TAG\|ALGO}}=TIMEEV.