Nudged elastic bands - Revision history

Wolloch: /* Possible issues and advice on how to address it */

2025-04-11T10:05:01Z

Possible issues and advice on how to address it

← Older revision		Revision as of 10:05, 11 April 2025
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	Failing to do so introduces artificial forces, causing the images to drift apart.		Failing to do so introduces artificial forces, causing the images to drift apart.
	While this does not affect the VASP calculations, it can complicate result visualization.		While this does not affect the VASP calculations, it can complicate result visualization.
	{{NB\|tip\|For more advanced calculations, consider using the [https://~~theory~~.cm.~~utexas.edu~~/~~vtsttools~~/ Transition State Tools for VASP].}}		{{NB\|tip\|For more advanced calculations, consider using the [https://vtstools.readthedocs.io/en/latest/index.html Transition State Tools for VASP].}}

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

Huebsch: Huebsch moved page Construction:Nudged elastic bands to Nudged elastic bands without leaving a redirect

2023-10-20T11:26:49Z

Huebsch moved page Construction:Nudged elastic bands to Nudged elastic bands without leaving a redirect

← Older revision	Revision as of 11:26, 20 October 2023
(No difference)

Huebsch at 11:25, 20 October 2023

2023-10-20T11:25:48Z

Schlipf at 10:18, 20 October 2023

2023-10-20T10:18:14Z

← Older revision		Revision as of 10:18, 20 October 2023
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	<references/>		<references/>

	[[Category:Transition states]][[Category:Howto]]		[[Category:Transition states]][[Category:Ionic minimization]][[Category:Howto]]

Schlipf: /* Step 2 */

2023-10-20T10:05:43Z

Step 2

← Older revision		Revision as of 10:05, 20 October 2023
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	These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.		These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.
	Place the {{FILE\|POSCAR}} files corresponding to these intermediate structures in subdirectories 01, 02, ...		Place the {{FILE\|POSCAR}} files corresponding to these intermediate structures in subdirectories 01, 02, ...
	{{NB\|mind\|It is highly recommended to minimize the number of images used to an absolute minimum. Convergence to the ground state is faster with fewer images. Starting with a single image between the two endpoints and increasing the number of images after the initial run has converged is often a prudent approach.}}		{{NB\|mind\|Make sure that the {{FILE\|POSCAR}} contains the same ordering or elements for initial, final and intermediate states. It is highly recommended to minimize the number of images used to an absolute minimum. Convergence to the ground state is faster with fewer images. Starting with a single image between the two endpoints and increasing the number of images after the initial run has converged is often a prudent approach.}}

	==== Step 3 ====		==== Step 3 ====

Schlipf at 09:49, 20 October 2023

2023-10-20T09:49:49Z

← Older revision		Revision as of 09:49, 20 October 2023
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	<references/>		<references/>

	[[Category:Transition ~~States~~]][[Category:Howto]]		[[Category:Transition states]][[Category:Howto]]

Schlipf at 09:38, 20 October 2023

2023-10-20T09:38:16Z

← Older revision		Revision as of 09:38, 20 October 2023
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	== How to set up an NEB calculation ==		== How to set up an NEB calculation ==

	~~First, carefully~~ converge the fixed structures of your elastic band, i.e., the initial and the final state.		==== Step 1 ====
	Remember that in the subsequent steps, the elastic band will be attached to these ~~fixpoints~~ so any error will affect the transition path you obtain.		Carefully converge the fixed structures of your elastic band, i.e., the initial and the final state.
			Remember that in the subsequent steps, the elastic band will be attached to these fixed structures so any error will affect the transition path you obtain.

	~~Secondly, construct~~ an initial guess for the intermediate structures.		==== Step 2 ====
	You may use a script like in the [[~~https://www.vasp.at/wiki/index.php/Collective_jumps_of_a_Pt_adatom_on_fcc~~-~~Pt_~~(001):~~_Nudged_Elastic_Band_Calculation~~\|tutorial]] or ~~come up with~~ your method.		Construct an initial guess for the intermediate structures.
			You may use a script like in the [[Collective jumps of a Pt adatom on fcc-Pt (001): Nudged Elastic Band Calculation\|tutorial]] or develop your own method.
	This script in the tutorial also offers the option to remove center-of-mass motion.		This script in the tutorial also offers the option to remove center-of-mass motion.
	These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.		These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.
Line 16:		Line 18:
	{{NB\|mind\|It is highly recommended to minimize the number of images used to an absolute minimum. Convergence to the ground state is faster with fewer images. Starting with a single image between the two endpoints and increasing the number of images after the initial run has converged is often a prudent approach.}}		{{NB\|mind\|It is highly recommended to minimize the number of images used to an absolute minimum. Convergence to the ground state is faster with fewer images. Starting with a single image between the two endpoints and increasing the number of images after the initial run has converged is often a prudent approach.}}

	~~Thirdly, create~~ an {{FILE\|INCAR}} file in the root directory and set the tag {{TAG\|IMAGES}} to the number of intermediate structures.		==== Step 3 ====
			Create an {{FILE\|INCAR}} file in the root directory and set the tag {{TAG\|IMAGES}} to the number of intermediate structures.
	This will introduce tangential springs to maintain equidistance among images during the relaxation process.		This will introduce tangential springs to maintain equidistance among images during the relaxation process.
	You can control the strength with the {{TAG\|SPRING}} tag, where negative values (like the default of -5) activate the NEB method.		You can control the strength with the {{TAG\|SPRING}} tag, where negative values (like the default of -5) activate the NEB method.
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	You should also set {{TAG\|IBRION}}, {{TAG\|ISIF}}, {{TAG\|NSW}}, and other relaxation-related tags.		You should also set {{TAG\|IBRION}}, {{TAG\|ISIF}}, {{TAG\|NSW}}, and other relaxation-related tags.

	~~Fourthly, create~~ the remaining input files {{FILE\|KPOINTS}} and {{FILE\|POTCAR}}.		==== Step 4 ====
			Create the remaining input files {{FILE\|KPOINTS}} and {{FILE\|POTCAR}}.
	For the NEB method, we recommend that all input files, except the {{TAG\|POSCAR}}, {{TAG\|WAVECAR}} and {{TAG\|CHGCAR}} file, reside in the root directory.		For the NEB method, we recommend that all input files, except the {{TAG\|POSCAR}}, {{TAG\|WAVECAR}} and {{TAG\|CHGCAR}} file, reside in the root directory.
	Then run VASP until the path is optimized.		Then run VASP until the path is optimized.
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	== Possible issues and advice on how to address it ==		== Possible issues and advice on how to address it ==
	One challenge with the NEB method arises from its non-linear constraint, ~~where~~ movements ~~are restricted~~ to ~~the~~ hyper-plane perpendicular to the current tangent.		One challenge with the NEB method arises from its non-linear constraint, which restricts movements to a hyper-plane perpendicular to the current tangent.
	This characteristic can lead to convergence issues with the Conjugate Gradient (CG) algorithm ({{TAG\|IBRION}}=2).		This characteristic can lead to convergence issues with the Conjugate Gradient (CG) algorithm ({{TAG\|IBRION}}=2).
	In such cases, it is advisable to use alternative algorithms like the RMM-DIIS algorithm ({{TAG\|IBRION}}=1) or the quick-min algorithm ({{TAG\|IBRION}}=3).		In such cases, it is advisable to use alternative algorithms like the RMM-DIIS algorithm ({{TAG\|IBRION}}=1) or the quick-min algorithm ({{TAG\|IBRION}}=3).
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	While this does not affect the VASP calculations, it can complicate result visualization.		While this does not affect the VASP calculations, it can complicate result visualization.

	{{NB\|tip\|~~If you want to run~~ more advanced calculations, ~~you may~~ consider the [https://theory.cm.utexas.edu/vtsttools/ Transition State Tools for VASP].}}		{{NB\|tip\|For more advanced calculations, consider using the [https://theory.cm.utexas.edu/vtsttools/ Transition State Tools for VASP].}}

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

Schlipf at 09:31, 20 October 2023

2023-10-20T09:31:15Z

← Older revision		Revision as of 09:31, 20 October 2023
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	The nudged elastic band (NEB) method{{cite\|mills:surf-sci:1995}}{{cite\|jonsson:book:1998}} is a computational technique ~~to study the~~ energy ~~landscape~~ and reaction pathways of chemical reactions or phase transitions.		The nudged elastic band (NEB) method{{cite\|mills:surf-sci:1995}}{{cite\|jonsson:book:1998}} is a computational technique used for studying energy landscapes and reaction pathways in chemical reactions or phase transitions.
	It ~~involves the construction of~~ an initial path connecting the initial and final states ~~of a system~~, ~~with~~ a series of ''images'' ~~representing~~ intermediate configurations.		It entails creating an initial path connecting the system's initial and final states, employing a series of ''images'' to represent intermediate configurations.
	These images are ~~connected~~ by springs, ~~which create~~ an elastic band.		These images are linked by springs, forming an elastic band.
	The method then iteratively adjusts the positions ~~of the images~~ along the band, ~~while~~ minimizing ~~the~~ energy, until a minimum energy pathway (the "nudged" path) is ~~found~~.		The method then iteratively adjusts the image positions along the band, minimizing energy until a minimum energy pathway, known as the 'nudged' path, is achieved.

	== How to set up an NEB calculation ==		== How to set up an NEB calculation ==

Schlipf at 09:28, 20 October 2023

2023-10-20T09:28:32Z

Schlipf at 09:25, 20 October 2023

2023-10-20T09:25:14Z

← Older revision		Revision as of 09:25, 20 October 2023
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	== How-to set up a NEB calculation ==		== How-to set up a NEB calculation ==

	~~The nudged~~ elastic band ~~(NEB) method is a technique used to calculate energy barriers in VASP~~. ~~When employing this method~~, the ~~SPRING parameter is set to a negative value (e.g~~., ~~SPRING= -5), which is~~ the ~~recommended setting. This negative value introduces additional tangential springs~~ to ~~maintain equidistance among images during~~ the ~~relaxation process. It is important not to use excessively large values for SPRING, as it can hinder convergence. The default value generally provides reliable results~~.		First, carefully converge the fixed structures of your elastic band, i.e., the initial and the final state.
			Remember that in the subsequent steps, the elastic band will be attached to these fixpoints so any error will affect the transition path you obtain.

	~~One challenge with the NEB method arises from its non-linear constraint~~, ~~where movements are restricted to~~ the ~~hyper-plane perpendicular to the current tangent~~. ~~This characteristic can lead to convergence issues with the Conjugate Gradient (CG) algorithm. In such cases, it is advisable to~~ use ~~alternative algorithms~~ like the ~~RMM~~-~~DIIS algorithm~~ (~~IBRION=1~~) or the ~~quick~~-~~min algorithm (IBRION=3)~~. ~~Additionally~~, the ~~equidistant~~ images ~~tend~~ to ~~deviate from this constraint in~~ the ~~initial steps~~. ~~To address this, applying~~ a ~~low dimensionality parameter (IBRION=1, NFREE=2) in~~ the ~~initial steps or using steepest descent minimization without line optimization (IBRION=3, SMASS=2) can help pre-converge~~ the images.		Secondly, construct an initial guess for the intermediate structures.
			You may use a script like in the [[https://www.vasp.at/wiki/index.php/Collective_jumps_of_a_Pt_adatom_on_fcc-Pt_(001):_Nudged_Elastic_Band_Calculation\|tutorial]] or come of with your method.
			This script in the tutorial also offers the option to remove center-of-mass motion.
			These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.
			Place the {{FILE\|POSCAR}} files corresponding to these intermediate structures in subdirectories 01, 02, ...
			{{NB\|mind\|It is highly recommended to minimize the number of images used to an absolute minimum. Convergence to the ground state is faster with fewer images. Starting with a single image between the two endpoints and increasing the number of images after the initial run has converged is often a prudent approach.}}

	~~If all degrees of freedom are allowed to relax (e.g.~~, in ~~isolated molecules or surfaces), it is crucial~~ to ~~ensure that~~ the ~~sum~~ of ~~all positions remains consistent across all cells~~. ~~Failing~~ to ~~do so introduces artificial forces, causing~~ the ~~images to drift apart~~. ~~While this doesn't affect~~ the ~~VASP calculations~~, ~~it can complicate result visualization~~. ~~Often, an initial linearly interpolated starting guess~~ is ~~appropriate~~, ~~which~~ can ~~be achieved using a script called interpolatePOS~~. ~~This script~~ also ~~offers the option to remove center-of-mass motion~~.		Thirdly, create an {{FILE\|INCAR}} file in the root directory and set the tag {{TAG\|IMAGES}} to the number of intermediate structures.
			This will introduce tangential springs to maintain equidistance among images during the relaxation process.
			You can control the strength with the {{TAG\|SPRING}} tag, where negative values (like the default of -5) activate the NEB method.
			It is important not to use excessively large values for {{TAG\|SPRING}}, as it can hinder convergence.
			The default value generally provides reliable results.
			You should also set {{TAG\|IBRION}}, {{TAG\|ISIF}}, {{TAG\|NSW}}, and other relaxation related tags.

	~~It is highly recommended to minimize~~ the ~~number of images used to an absolute minimum~~. ~~Convergence to~~ the ~~ground state is faster with fewer images. Starting with a single image between~~ the ~~two endpoints~~ and ~~increasing~~ the ~~number of images after~~ the ~~initial run has converged~~ is ~~often a prudent approach~~.		Fourthly, create the remaining input files {{FILE\|KPOINTS}} and {{FILE\|POTCAR}}.
			For the NEB method, we recommend that all input files, except the {{TAG\|POSCAR}}, {{TAG\|WAVECAR}} and {{TAG\|CHGCAR}} file, reside in the root directory.
			Then run VASP until the path is optimized.

	~~For~~ the ~~nudged elastic band~~ method, it is ~~recommended that all input files~~, ~~except~~ the {{TAG\|~~POSCAR~~}}, {{TAG\|~~WAVECAR~~}} ~~and~~ {{TAG\|~~CHGCAR~~}} ~~file~~, ~~reside~~ in the ~~root directory~~.
			== Possible issues and advice how to address it ==
			One challenge with the NEB method arises from its non-linear constraint, where movements are restricted to the hyper-plane perpendicular to the current tangent.
			This characteristic can lead to convergence issues with the Conjugate Gradient (CG) algorithm ({{TAG\|IBRION}}=2).
			In such cases, it is advisable to use alternative algorithms like the RMM-DIIS algorithm ({{TAG\|IBRION}}=1) or the quick-min algorithm ({{TAG\|IBRION}}=3).
			Additionally, the equidistant images tend to deviate from this constraint in the initial steps.
			To address this, applying a low dimensionality parameter ({{TAG\|IBRION}}=1, {{TAG\|NFREE}}=2) in the initial steps or using steepest descent minimization without line optimization ({{TAG\|IBRION}}=3, {{TAG\|SMASS}}=2) can help pre-converge the images.

			If all degrees of freedom are allowed to relax (e.g., in isolated molecules or surfaces), it is crucial to ensure that the sum of all positions remains consistent across all cells.
			Failing to do so introduces artificial forces, causing the images to drift apart.
			While this does not affect the VASP calculations, it can complicate result visualization.

			{{NB\|tip\|If you want to run more advanced calculations, you may consider the [https://theory.cm.utexas.edu/vtsttools/ Transition State Tools for VASP].}}

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

← Older revision		Revision as of 11:25, 20 October 2023
Line 8:		Line 8:
	==== Step 1 ====		==== Step 1 ====
	Carefully converge the fixed structures of your elastic band, i.e., the initial and the final state.		Carefully converge the fixed structures of your elastic band, i.e., the initial and the final state.
	Remember that in the subsequent steps, the elastic band will be attached to these fixed structures so any error will affect the transition path you obtain.		Remember that in the subsequent steps, the elastic band will be attached to these fixed structures, so any error will affect the transition path you obtain.

	==== Step 2 ====		==== Step 2 ====
Line 14:		Line 14:
	You may use a script like in the [[Collective jumps of a Pt adatom on fcc-Pt (001): Nudged Elastic Band Calculation\|tutorial]] or develop your own method.		You may use a script like in the [[Collective jumps of a Pt adatom on fcc-Pt (001): Nudged Elastic Band Calculation\|tutorial]] or develop your own method.
	This script in the tutorial also offers the option to remove center-of-mass motion.		This script in the tutorial also offers the option to remove center-of-mass motion.
	These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.		These intermediate images should be somewhat close to the real transition path; otherwise, the optimization of the elastic band may fail.
	Place the {{FILE\|POSCAR}} files corresponding to these intermediate structures in subdirectories 01, 02, ...		Place the {{FILE\|POSCAR}} files corresponding to these intermediate structures in subdirectories 01, 02, etc.
	{{NB\|mind\|Make sure that the {{FILE\|POSCAR}} contains the same ordering or elements for initial, final and intermediate states. It is highly recommended to minimize the number of images used to an absolute minimum. Convergence to the ground state is faster with fewer images. Starting with a single image between the two endpoints and increasing the number of images after the initial run has converged is often a prudent approach.}}		{{NB\|mind\|Make sure that the {{FILE\|POSCAR}} contains the same ordering of elements for initial, final, and intermediate states. It is highly recommended to minimize the number of images used to an absolute minimum. Convergence to the ground state is faster with fewer images. Starting with a single image between the two endpoints and increasing the number of images after the initial run has converged is often a prudent approach.}}

	==== Step 3 ====		==== Step 3 ====
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	It is important not to use excessively large values for {{TAG\|SPRING}}, as it can hinder convergence.		It is important not to use excessively large values for {{TAG\|SPRING}}, as it can hinder convergence.
	The default value generally provides reliable results.		The default value generally provides reliable results.
	You should also set {{TAG\|IBRION}}, {{TAG\|ISIF}}, {{TAG\|NSW}}, and other relaxation-related tags.		You should also set {{TAG\|IBRION}}, {{TAG\|ISIF}}, {{TAG\|NSW}}, and other [[Category:Ionic minimization\|relaxation-related tags]].

	==== Step 4 ====		==== Step 4 ====
	Create the remaining input files {{FILE\|KPOINTS}} and {{FILE\|POTCAR}}.		Create the remaining input files {{FILE\|KPOINTS}} and {{FILE\|POTCAR}}.
	For the NEB method, we recommend that all input files, except the {{TAG\|POSCAR}}, {{TAG\|WAVECAR}} and {{TAG\|CHGCAR}} file, reside in the root directory.		For the NEB method, we recommend that all input files, except the {{TAG\|POSCAR}}, {{TAG\|WAVECAR}} and {{TAG\|CHGCAR}} file, reside in the root directory.
	Then run VASP until the path is optimized.		Then, run VASP until the path is optimized.


	== Possible issues and advice on how to address it ==		== Possible issues and advice on how to address it ==
	One challenge with the NEB method arises from its non-linear constraint, which restricts movements to a hyper-plane perpendicular to the current tangent.		One challenge with the NEB method arises from its non-linear constraint, which restricts movements to a hyper-plane perpendicular to the current tangent.
	This characteristic can lead to convergence issues with the ~~Conjugate Gradient~~ (CG) algorithm ({{TAG\|IBRION}}=2).		This characteristic can lead to convergence issues with the conjugate-gradient (CG) algorithm ({{TAG\|IBRION}}=2).
	In such cases, it is advisable to use alternative algorithms like the RMM-DIIS algorithm ({{TAG\|IBRION}}=1) or the quick-min algorithm ({{TAG\|IBRION}}=3).		In such cases, it is advisable to use alternative algorithms like the RMM-DIIS algorithm ({{TAG\|IBRION}}=1) or the quick-min algorithm ({{TAG\|IBRION}}=3).
	Additionally, the equidistant images tend to deviate from this constraint in the initial steps.		Additionally, the equidistant images tend to deviate from this constraint in the initial steps.
	To address this, applying a low dimensionality parameter ({{TAG\|IBRION}}=1, {{TAG\|NFREE}}=2) in the initial steps or using steepest descent minimization without line optimization ({{TAG\|IBRION}}=3, {{TAG\|SMASS}}=2) can help pre-converge the images.		To address this, applying a low dimensionality parameter ({{TAG\|IBRION}}=1, {{TAG\|NFREE}}=2) in the initial steps or using steepest descent minimization without line optimization ({{TAG\|IBRION}}=3, {{TAG\|SMASS}}=2) can help pre-converge the images.

	If all degrees of freedom are allowed to relax (e.g., in isolated molecules or surfaces), it is crucial to ensure that the sum of all positions remains consistent across all cells.		If all degrees of freedom are allowed to relax, (e.g., in isolated molecules or surfaces), it is crucial to ensure that the sum of all positions remains consistent across all cells.
	Failing to do so introduces artificial forces, causing the images to drift apart.		Failing to do so introduces artificial forces, causing the images to drift apart.
	While this does not affect the VASP calculations, it can complicate result visualization.		While this does not affect the VASP calculations, it can complicate result visualization.

	{{NB\|tip\|For more advanced calculations, consider using the [https://theory.cm.utexas.edu/vtsttools/ Transition State Tools for VASP].}}		{{NB\|tip\|For more advanced calculations, consider using the [https://theory.cm.utexas.edu/vtsttools/ Transition State Tools for VASP].}}

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	[[TS search using the NEB Method]]		[[TS search using the NEB Method]]

	== References ==		== References ==
	<references/>		<references/>

	[[Category:Transition states]][[Category:Ionic minimization]][[Category:Howto]]		[[Category:Transition states]][[Category:Ionic minimization]][[Category:Howto]]

← Older revision		Revision as of 09:28, 20 October 2023
Line 4:		Line 4:
	The method then iteratively adjusts the positions of the images along the band, while minimizing the energy, until a minimum energy pathway (the "nudged" path) is found.		The method then iteratively adjusts the positions of the images along the band, while minimizing the energy, until a minimum energy pathway (the "nudged" path) is found.

	== How-to set up a NEB calculation ==		== How to set up an NEB calculation ==

	First, carefully converge the fixed structures of your elastic band, i.e., the initial and the final state.		First, carefully converge the fixed structures of your elastic band, i.e., the initial and the final state.
Line 10:		Line 10:

	Secondly, construct an initial guess for the intermediate structures.		Secondly, construct an initial guess for the intermediate structures.
	You may use a script like in the [[https://www.vasp.at/wiki/index.php/Collective_jumps_of_a_Pt_adatom_on_fcc-Pt_(001):_Nudged_Elastic_Band_Calculation\|tutorial]] or come of with your method.		You may use a script like in the [[https://www.vasp.at/wiki/index.php/Collective_jumps_of_a_Pt_adatom_on_fcc-Pt_(001):_Nudged_Elastic_Band_Calculation\|tutorial]] or come up with your method.
	This script in the tutorial also offers the option to remove center-of-mass motion.		This script in the tutorial also offers the option to remove center-of-mass motion.
	These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.		These intermediate images should be somewhat close to the real transition path otherwise the optimization of the elastic band may fail.
Line 21:		Line 21:
	It is important not to use excessively large values for {{TAG\|SPRING}}, as it can hinder convergence.		It is important not to use excessively large values for {{TAG\|SPRING}}, as it can hinder convergence.
	The default value generally provides reliable results.		The default value generally provides reliable results.
	You should also set {{TAG\|IBRION}}, {{TAG\|ISIF}}, {{TAG\|NSW}}, and other relaxation related tags.		You should also set {{TAG\|IBRION}}, {{TAG\|ISIF}}, {{TAG\|NSW}}, and other relaxation-related tags.

	Fourthly, create the remaining input files {{FILE\|KPOINTS}} and {{FILE\|POTCAR}}.		Fourthly, create the remaining input files {{FILE\|KPOINTS}} and {{FILE\|POTCAR}}.
Line 28:		Line 28:


	== Possible issues and advice how to address it ==		== Possible issues and advice on how to address it ==
	One challenge with the NEB method arises from its non-linear constraint, where movements are restricted to the hyper-plane perpendicular to the current tangent.		One challenge with the NEB method arises from its non-linear constraint, where movements are restricted to the hyper-plane perpendicular to the current tangent.
	This characteristic can lead to convergence issues with the Conjugate Gradient (CG) algorithm ({{TAG\|IBRION}}=2).		This characteristic can lead to convergence issues with the Conjugate Gradient (CG) algorithm ({{TAG\|IBRION}}=2).