IBRION - Revision history

Schlipf at 10:07, 17 February 2025

2025-02-17T10:07:55Z

← Older revision		Revision as of 10:07, 17 February 2025
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	:::** {{TAG\|IBRION}}=44 [[improved dimer method]]		:::** {{TAG\|IBRION}}=44 [[improved dimer method]]

	:::* [[#~~User-~~supplied ~~interactive changes~~\|User-supplied interactive changes]]		:::* [[#Interactively supplied positions and lattice vectors\|User-supplied interactive changes]]
	:::** {{TAG\|IBRION}}=11 from standard input		:::** {{TAG\|IBRION}}=11 from standard input
	:::** {{TAG\|IBRION}}=12 from Python plugin		:::** {{TAG\|IBRION}}=12 from Python plugin

Huebsch: /* Interactively supplied positions and lattice vectors */

2025-01-07T11:06:55Z

Interactively supplied positions and lattice vectors

← Older revision		Revision as of 11:06, 7 January 2025
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	* With {{TAGO\|IBRION\|11}}, you can provide new structures via the standard input. For {{TAG\|ISIF}}>=3, a complete {{FILE\|POSCAR}} file is read, otherwise just the positions in fractional coordinates.		* With {{TAGO\|IBRION\|11}}, you can provide new structures via the standard input. For {{TAG\|ISIF}}>=3, a complete {{FILE\|POSCAR}} file is read, otherwise just the positions in fractional coordinates.

	* If you [[Makefile.include#Plugins_(optional)\|linked VASP with Python]], you can [[~~Writing a Python plugin~~\|write a Python plugin]] to modify the structure. Set {{TAGO\|IBRION\|12}} or {{TAGO\|PLUGINS/STRUCTURE\|T}} to activate it.		* If you [[Makefile.include#Plugins_(optional)\|linked VASP with Python]], you can [[Plugins\|write a Python plugin]] to modify the structure. Set {{TAGO\|IBRION\|12}} or {{TAGO\|PLUGINS/STRUCTURE\|T}} to activate it.

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

Huebsch at 11:06, 7 January 2025

2025-01-07T11:06:33Z

← Older revision		Revision as of 11:06, 7 January 2025
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	* With {{TAGO\|IBRION\|11}}, you can provide new structures via the standard input. For {{TAG\|ISIF}}>=3, a complete {{FILE\|POSCAR}} file is read, otherwise just the positions in fractional coordinates.		* With {{TAGO\|IBRION\|11}}, you can provide new structures via the standard input. For {{TAG\|ISIF}}>=3, a complete {{FILE\|POSCAR}} file is read, otherwise just the positions in fractional coordinates.

	~~<!--~~
	* If you [[Makefile.include#Plugins_(optional)\|linked VASP with Python]], you can [[Writing a Python plugin\|write a Python plugin]] to modify the structure. Set {{TAGO\|IBRION\|12}} or {{TAGO\|PLUGINS/STRUCTURE\|T}} to activate it.		* If you [[Makefile.include#Plugins_(optional)\|linked VASP with Python]], you can [[Writing a Python plugin\|write a Python plugin]] to modify the structure. Set {{TAGO\|IBRION\|12}} or {{TAGO\|PLUGINS/STRUCTURE\|T}} to activate it.
	~~-->~~

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

Huebsch: /* Related tags and articles */

2025-01-07T11:05:51Z

Huebsch: /* Computing the phonon modes */

2024-10-18T12:53:07Z

Computing the phonon modes

← Older revision		Revision as of 12:53, 18 October 2024
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	== Computing the phonon modes ==		== Computing the phonon modes ==

	The second-order derivatives of the total energy <math>E</math> with respect to ionic positions <math>R_{\alpha i}</math> of ion <math>\alpha</math> in the direction of <math>i</math>, is computed using a first-order derivative of the [[forces]] <math>F_{\beta j}</math>. Then, the dynamical matrix <math>D_{\alpha i \beta j}</math> is constructed, diagonalized, and the phonon modes and frequencies of the system are reported in the {{FILE\|OUTCAR}} file and {{FILE\|vaspout.h5}}. Also see [[Phonons: Theory\|theory on phonons]].		The second-order derivatives of the total energy <math>E</math> with respect to ionic positions <math>R_{\alpha i}</math> of ion <math>\alpha</math> in the direction <math>i</math>, is computed using a first-order derivative of the [[forces]] <math>F_{\beta j}</math>. Then, the dynamical matrix <math>D_{\alpha i \beta j}</math> is constructed, diagonalized, and the phonon modes and frequencies of the system are reported in the {{FILE\|OUTCAR}} file and {{FILE\|vaspout.h5}}. Also see [[Phonons: Theory\|theory on phonons]].
	{{NB\|tip\|It ~~is often~~ necessary to set {{TAGO\|EDIFF\|<= 1E-6}} because the default ({{TAGO\|EDIFF\|1E-4}}) often results in unacceptably large errors.}}		{{NB\|tip\|It may be necessary to set {{TAGO\|EDIFF\|<= 1E-6}} because the default ({{TAGO\|EDIFF\|1E-4}}) often results in unacceptably large errors.}}
	VASP implements two different methods to compute the phonon modes and can use symmetry to reduce the number of computed displacements:		VASP implements two different methods to compute the phonon modes and can use symmetry to reduce the number of computed displacements:

Schlipf: /* User-supplied interactive changes to positions and lattice vectors */

2024-10-18T11:07:29Z

User-supplied interactive changes to positions and lattice vectors

← Older revision		Revision as of 11:07, 18 October 2024
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	* The [[nudged elastic bands]] method finds an approximate reaction path based on the initial and final structure, i.e., reactant and product.		* The [[nudged elastic bands]] method finds an approximate reaction path based on the initial and final structure, i.e., reactant and product.

	== ~~User-~~supplied ~~interactive changes to~~ positions and lattice vectors ==		== Interactively supplied positions and lattice vectors ==

	Occasionally, you may want to run VASP for related structures where the overhead of restarting VASP is significant.		Occasionally, you may want to run VASP for related structures where the overhead of restarting VASP is significant.

Schlipf: /* User-supplied interactive changes to positions and lattice vectors */

2024-10-18T11:05:02Z

User-supplied interactive changes to positions and lattice vectors

← Older revision		Revision as of 11:05, 18 October 2024
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	* With {{TAGO\|IBRION\|11}}, you can provide new structures via the standard input. For {{TAG\|ISIF}}>=3, a complete {{FILE\|POSCAR}} file is read, otherwise just the positions in fractional coordinates.		* With {{TAGO\|IBRION\|11}}, you can provide new structures via the standard input. For {{TAG\|ISIF}}>=3, a complete {{FILE\|POSCAR}} file is read, otherwise just the positions in fractional coordinates.

			<!--
	* If you [[Makefile.include#Plugins_(optional)\|linked VASP with Python]], you can [[Writing a Python plugin\|write a Python plugin]] to modify the structure. Set {{TAGO\|IBRION\|12}} or {{TAGO\|PLUGINS/STRUCTURE\|T}} to activate it.		* If you [[Makefile.include#Plugins_(optional)\|linked VASP with Python]], you can [[Writing a Python plugin\|write a Python plugin]] to modify the structure. Set {{TAGO\|IBRION\|12}} or {{TAGO\|PLUGINS/STRUCTURE\|T}} to activate it.
			-->

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

Schlipf: Split how-to part of IBRION into new page "structure optimization"

2024-10-18T11:04:29Z

Split how-to part of IBRION into new page "structure optimization"

Show changes

Csheldon: /* IBRION=1: ionic relaxation (RMM-DIIS). */

2024-07-10T08:29:07Z

IBRION=1: ionic relaxation (RMM-DIIS).

← Older revision		Revision as of 08:29, 10 July 2024
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	#If {{TAG\|NFREE}} is not specified, the criterion whether information is removed from the iteration history is based on the eigenvalue spectrum of the inverse Hessian matrix: if one eigenvalue of the inverse Hessian matrix is larger than 8, information from previous steps is discarded.		#If {{TAG\|NFREE}} is not specified, the criterion whether information is removed from the iteration history is based on the eigenvalue spectrum of the inverse Hessian matrix: if one eigenvalue of the inverse Hessian matrix is larger than 8, information from previous steps is discarded.

	For complex problems {{TAG\|NFREE}} can usually be set to a rather large value (i.e. 10-20), however systems of low dimensionality require a ~~carful~~ setting of {{TAG\|NFREE}} (or preferably an exact counting of the number of degrees of freedom). To increase {{TAG\|NFREE}} beyond 20 rarely improves convergence. If {{TAG\|NFREE}} is set to too large, the RMM-DIIS algorithm might diverge.		For complex problems {{TAG\|NFREE}} can usually be set to a rather large value (i.e. 10-20), however systems of low dimensionality require a careful setting of {{TAG\|NFREE}} (or preferably an exact counting of the number of degrees of freedom). To increase {{TAG\|NFREE}} beyond 20 rarely improves convergence. If {{TAG\|NFREE}} is set to too large, the RMM-DIIS algorithm might diverge.

	The choice of a reasonable {{TAG\|POTIM}} is also important and can speed up calculations significantly, we recommend to find an optimal {{TAG\|POTIM}} using {{TAG\|IBRION}}=2 or performing a few test calculations (see below).		The choice of a reasonable {{TAG\|POTIM}} is also important and can speed up calculations significantly, we recommend to find an optimal {{TAG\|POTIM}} using {{TAG\|IBRION}}=2 or performing a few test calculations (see below).

Csheldon: /* IBRION=1: ionic relaxation (RMM-DIIS). */

2024-07-10T08:28:26Z

IBRION=1: ionic relaxation (RMM-DIIS).

← Older revision		Revision as of 08:28, 10 July 2024
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	The implemented algorithm is called RMM-DIIS.{{cite\|pulay:cpl:1980}} It implicitly calculates an approximation of the inverse Hessian matrix by taking into account information from previous iterations. On startup, the initial Hessian matrix is diagonal and equal to {{TAG\|POTIM}}. Information from old steps (which can lead to linear dependencies) is automatically removed from the iteration history, if required. The number of vectors kept in the iterations history (which corresponds to the rank of the Hessian matrix must not exceed the degrees of freedom. Naively the number of degrees of freedom is 3(NIONS-1). But symmetry arguments or constraints can reduce this number significantly.		The implemented algorithm is called RMM-DIIS.{{cite\|pulay:cpl:1980}} It implicitly calculates an approximation of the inverse Hessian matrix by taking into account information from previous iterations. On startup, the initial Hessian matrix is diagonal and equal to {{TAG\|POTIM}}. Information from old steps (which can lead to linear dependencies) is automatically removed from the iteration history, if required. The number of vectors kept in the iterations history (which corresponds to the rank of the Hessian matrix must not exceed the degrees of freedom. Naively the number of degrees of freedom is 3(NIONS-1). But symmetry arguments or constraints can reduce this number significantly.

	There are two algorithms ~~build~~ in to remove information from the iteration history:		There are two algorithms built in to remove information from the iteration history:
	#If {{TAG\|NFREE}} is set in the {{FILE\|INCAR}} file, only up to {{TAG\|NFREE}} ionic steps are kept in the iteration history (the rank of the approximate Hessian matrix is not larger than {{TAG\|NFREE}}).		#If {{TAG\|NFREE}} is set in the {{FILE\|INCAR}} file, only up to {{TAG\|NFREE}} ionic steps are kept in the iteration history (the rank of the approximate Hessian matrix is not larger than {{TAG\|NFREE}}).
	#If {{TAG\|NFREE}} is not specified, the criterion whether information is removed from the iteration history is based on the eigenvalue spectrum of the inverse Hessian matrix: if one eigenvalue of the inverse Hessian matrix is larger than 8, information from previous steps is discarded.		#If {{TAG\|NFREE}} is not specified, the criterion whether information is removed from the iteration history is based on the eigenvalue spectrum of the inverse Hessian matrix: if one eigenvalue of the inverse Hessian matrix is larger than 8, information from previous steps is discarded.

← Older revision		Revision as of 10:07, 17 February 2025
Line 24:		Line 24:
	:::** {{TAG\|IBRION}}=44 [[improved dimer method]]		:::** {{TAG\|IBRION}}=44 [[improved dimer method]]

	:::* [[#~~User-~~supplied ~~interactive changes~~\|User-supplied interactive changes]]		:::* [[#Interactively supplied positions and lattice vectors\|User-supplied interactive changes]]
	:::** {{TAG\|IBRION}}=11 from standard input		:::** {{TAG\|IBRION}}=11 from standard input
	:::** {{TAG\|IBRION}}=12 from Python plugin		:::** {{TAG\|IBRION}}=12 from Python plugin

← Older revision		Revision as of 11:05, 7 January 2025
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	[[IRC calculations]],		[[IRC calculations]],
	[[Improved Dimer Method]],		[[Improved Dimer Method]],
	[[Writing a Python plugin]]		[[Plugins\|Writing a Python plugin]]

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

	[[Category:INCAR tag]][[Category:Ionic minimization]][[Category:Molecular dynamics]][[Category:Phonons]][[Category:Transition states]]		[[Category:INCAR tag]][[Category:Ionic minimization]][[Category:Molecular dynamics]][[Category:Phonons]][[Category:Transition states]]

← Older revision		Revision as of 08:29, 10 July 2024
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	#If {{TAG\|NFREE}} is not specified, the criterion whether information is removed from the iteration history is based on the eigenvalue spectrum of the inverse Hessian matrix: if one eigenvalue of the inverse Hessian matrix is larger than 8, information from previous steps is discarded.		#If {{TAG\|NFREE}} is not specified, the criterion whether information is removed from the iteration history is based on the eigenvalue spectrum of the inverse Hessian matrix: if one eigenvalue of the inverse Hessian matrix is larger than 8, information from previous steps is discarded.

	For complex problems {{TAG\|NFREE}} can usually be set to a rather large value (i.e. 10-20), however systems of low dimensionality require a ~~carful~~ setting of {{TAG\|NFREE}} (or preferably an exact counting of the number of degrees of freedom). To increase {{TAG\|NFREE}} beyond 20 rarely improves convergence. If {{TAG\|NFREE}} is set to too large, the RMM-DIIS algorithm might diverge.		For complex problems {{TAG\|NFREE}} can usually be set to a rather large value (i.e. 10-20), however systems of low dimensionality require a careful setting of {{TAG\|NFREE}} (or preferably an exact counting of the number of degrees of freedom). To increase {{TAG\|NFREE}} beyond 20 rarely improves convergence. If {{TAG\|NFREE}} is set to too large, the RMM-DIIS algorithm might diverge.

	The choice of a reasonable {{TAG\|POTIM}} is also important and can speed up calculations significantly, we recommend to find an optimal {{TAG\|POTIM}} using {{TAG\|IBRION}}=2 or performing a few test calculations (see below).		The choice of a reasonable {{TAG\|POTIM}} is also important and can speed up calculations significantly, we recommend to find an optimal {{TAG\|POTIM}} using {{TAG\|IBRION}}=2 or performing a few test calculations (see below).