VCAIMAGES - Revision history

Csheldon at 11:37, 20 March 2026

2026-03-20T11:37:46Z

← Older revision		Revision as of 11:37, 20 March 2026
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	Description: The tag {{TAG\|VCAIMAGES}} allows to perform thermodynamic integrations (TI); it defines the coupling parameter λ.		Description: The tag {{TAG\|VCAIMAGES}} allows to perform thermodynamic integrations (TI); it defines the coupling parameter λ.
	----		----
	{{TAG\|VCAIMAGES}} allows two molecular dynamics (MD) simulations to be performed with e.g. different {{TAG\|POTCAR}} or {{TAG\|KPOINTS}} files or different exchange-correlation functionals, and averages the energies and forces between the two calculations {{cite\|dorner:PRL:2018}}.		{{TAG\|VCAIMAGES}} allows two molecular dynamics (MD) simulations to be performed with e.g. different {{TAG\|POTCAR}} or {{TAG\|KPOINTS}} files or different exchange-correlation functionals, and averages the energies and forces between the two calculations. This is known as thermodynamic integration (TI) {{cite\|dorner:PRL:2018}}.

	The tag {{TAG\|VCAIMAGES}} internally splits the available nodes into two groups, and each group then performs an independent VASP calculation (this implies {{TAG\|VCAIMAGES}} only works in the MPI version). This behavior is implemented in the same way as the [[Nudged elastic bands \| nudged elastic band method]] (NEB) described under the tag {{TAG\|IMAGES}}. As opposed to NEB, only two images are created ({{TAG\|IMAGES}}=2 is set internally). The two calculations are performed in subdirectories <code>01</code> and <code>02</code> (<code>00</code> and <code>03</code> are not required, in contrast to NEB).		The tag {{TAG\|VCAIMAGES}} internally splits the available nodes into two groups, and each group then performs an independent VASP calculation (this implies {{TAG\|VCAIMAGES}} only works in the MPI version). This behavior is implemented in the same way as the [[Nudged elastic bands \| nudged elastic band method]] (NEB) described under the tag {{TAG\|IMAGES}}. As opposed to NEB, only two images are created ({{TAG\|IMAGES}}=2 is set internally). The two calculations are performed in subdirectories <code>01</code> and <code>02</code> (<code>00</code> and <code>03</code> are not required, in contrast to NEB).

Csheldon at 11:37, 20 March 2026

2026-03-20T11:37:22Z

← Older revision		Revision as of 11:37, 20 March 2026
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	{{TAGDEF\|VCAIMAGES\|[real]\|-1}}		{{TAGDEF\|VCAIMAGES\|[real]\|-1}}

	Description: The tag {{TAG\|VCAIMAGES}} allows to perform thermodynamic ~~coupling constant~~ integrations. To achieve this, two molecular dynamics simulations are performed with e.g. different {{TAG\|POTCAR}} or {{TAG\|KPOINTS}} files or different exchange-correlation functionals, and force averaging between the ~~two calculations is done{{cite\|dorner:PRL:2018}}~~.		Description: The tag {{TAG\|VCAIMAGES}} allows to perform thermodynamic integrations (TI); it defines the coupling parameter λ.
	----		----
	~~The tag~~ {{TAG\|VCAIMAGES}} ~~internally splits the available nodes into~~ two ~~groups, and each group~~		{{TAG\|VCAIMAGES}} allows two molecular dynamics (MD) simulations to be performed with e.g. different {{TAG\|POTCAR}} or {{TAG\|KPOINTS}} files or different exchange-correlation functionals, and averages the energies and forces between the two calculations {{cite\|dorner:PRL:2018}}.
	~~then performs an independent VASP calculation~~ (~~this implies~~ {{TAG\|~~VCAIMAGES~~}} ~~only works in the MPI version).~~
	~~This behavior is implemented in the same way as~~
	~~the nudged elastic band method described under the tag~~ {{TAG\|~~IMAGES~~}}~~. As opposed to~~ the ~~nudged~~
	~~elastic band method, VASP creates always~~ two ~~images by setting the tag~~ {{~~TAG~~\|~~IMAGES~~}}~~=2 internally.~~
	~~The two calculations are performed in subdirectories 01 and 02 (as opposed to the nudged elastic~~
	~~band method, subdirectories 00 and 03 are not required). A precise description of the file~~
	~~reading and writing is given below~~.

	The two VASP calculations are essentially ~~performed~~ independently in subdirectories 01 and 02.		The tag {{TAG\|VCAIMAGES}} internally splits the available nodes into two groups, and each group then performs an independent VASP calculation (this implies {{TAG\|VCAIMAGES}} only works in the MPI version). This behavior is implemented in the same way as the [[Nudged elastic bands \| nudged elastic band method]] (NEB) described under the tag {{TAG\|IMAGES}}. As opposed to NEB, only two images are created ({{TAG\|IMAGES}}=2 is set internally). The two calculations are performed in subdirectories <code>01</code> and <code>02</code> (<code>00</code> and <code>03</code> are not required, in contrast to NEB).
	The forces, energies and the stress tensor of the two calculations are averaged according to the ~~tag~~ {{TAG\|VCAIMAGES}}.
	Specifically, the value supplied in the tag {{TAG\|VCAIMAGES}} determines the weight of the calculations		=== Description of reading a writing during the calculation ===
	performed in subdirectory 01. The weight of the second image is 1-{{TAG\|VCAIMAGES}}. ~~The averaging~~		The two calculations are performed essentially independently in subdirectories <code>01</code> and <code>02</code>. The forces, energies, and the stress tensor of the two calculations are averaged according to the coupling parameter supplied by {{TAG\|VCAIMAGES}}. Specifically, the value supplied in the tag {{TAG\|VCAIMAGES}} determines the weight of the calculations performed in subdirectory <code>01</code>. The weight of the second image is 1-{{TAG\|VCAIMAGES}}. After self-consistency has been reach for both calculations, the energies and forces are averaged, affecting the final total energy as well as the forces. This ensures that the trajectories for the two MD simulations are identical.
	~~is performed after~~ self-consistency has been ~~reached~~ and ~~affects~~ the final total energy as well as		{{NB\|important\|Make sure that the initial {{FILE\|POSCAR}} is identical in both subdirectories.}}
	the forces. ~~Since the energies and forces are averaged,~~ the trajectories ~~generated by~~ the two simulations
	~~will be exactly~~ identical. Make sure ~~though,~~ that the initial {{~~TAG~~\|POSCAR}} ~~files~~ in the ~~two subdirectories~~		=== Finding the energies ===
	~~are exactly identical.~~ The averaged energies can be found in the {{TAG\|OUTCAR}} file after the lines		The averaged energies can be found in the {{TAG\|OUTCAR}} file after the lines
	"ENERGY OF THE ELECTRON-ION-THERMOSTAT SYSTEM (eV)", as well as in the file {{TAG\|OSZICAR}}		<code>ENERGY OF THE ELECTRON-ION-THERMOSTAT SYSTEM (eV)</code>, as well as in the file {{TAG\|OSZICAR}}
	(in the lines writing the free energy "F="). This ~~makes scanning~~ the {{~~TAG~~\|~~OSZICAR~~}} file for ~~the~~		(in the lines writing the free energy <code>F=</code>). This can make looking for the energies of the individual calculation awkward. You can find these under <code>FREE ENERGIE OF THE ION-ELECTRON SYSTEM (eV)</code> in the {{FILE\|OUTCAR}} file for a DFT calculation (They are under <code>ML FREE ENERGIE OF THE ION-ELECTRON SYSTEM (eV)</code> for a machine-learned force field (MLFF)).
	~~required energies of the individual calculations somewhat awkward~~.
	{{NB\|important\|In some cases it might be desirable to use a different number of cores for		{{NB\|important\|In some cases it might be desirable to use a different number of cores for
	the first image and the second image. ~~For instance~~, ~~this might be expedient for calculations~~		the first image and the second image. E.g., when the thermodynamic integration is performed from a coarse to a dense k-point grid, or from a cheap
	~~where~~ thermodynamic integration is performed from a coarse to a dense k-point grid, or from a cheap		to an expensive exchange-correlation functional. To set the number of cores in the first image the tag {{TAG\|NCORE_IN_IMAGE1}} has to be set. The second image then
	to an expensive exchange-correlation functional.
	To set the number of cores in the first image the tag {{TAG\|NCORE_IN_IMAGE1}} has to be set. The second image then
	contains the remaining cores.}}		contains the remaining cores.}}

	The usage of this tag is also explained in the supplementary information of reference {{cite\|dorner:PRL:2018}}.		The usage of this tag is also explained in the supplementary information of reference {{cite\|dorner:PRL:2018}}.

	== Related tags and articles ==		== Related tags and articles ==
	{{TAG\| NCORE_IN_IMAGE1}}, {{TAG\|SCALEE}}, {{TAG\| IMAGES}}		{{TAG\|NCORE_IN_IMAGE1}}, {{TAG\|SCALEE}}, {{TAG\|IMAGES}}

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

	~~<noinclude>~~
	~~----~~

	[[Category:INCAR tag]][[Category:Advanced molecular-dynamics sampling]]		[[Category:INCAR tag]][[Category:Advanced molecular-dynamics sampling]]

Csheldon at 11:12, 20 March 2026

2026-03-20T11:12:38Z

← Older revision		Revision as of 11:12, 20 March 2026
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	(in the lines writing the free energy "F="). This makes scanning the {{TAG\|OSZICAR}} file for the		(in the lines writing the free energy "F="). This makes scanning the {{TAG\|OSZICAR}} file for the
	required energies of the individual calculations somewhat awkward.		required energies of the individual calculations somewhat awkward.

	{{NB\|important\|In some cases it might be desirable to use a different number of cores for		{{NB\|important\|In some cases it might be desirable to use a different number of cores for
	the first image and the second image. For instance, this might be expedient for calculations		the first image and the second image. For instance, this might be expedient for calculations

Csheldon at 11:12, 20 March 2026

2026-03-20T11:12:32Z

← Older revision		Revision as of 11:12, 20 March 2026
Line 24:		Line 24:
	required energies of the individual calculations somewhat awkward.		required energies of the individual calculations somewhat awkward.

	~~Special handling:~~ In some cases it might be desirable to use a different number of cores for		{{NB\|important\|In some cases it might be desirable to use a different number of cores for
	the first image and the second image. For instance, this might be expedient for calculations		the first image and the second image. For instance, this might be expedient for calculations
	where thermodynamic integration is performed from a coarse to a dense k-point grid, or from a cheap		where thermodynamic integration is performed from a coarse to a dense k-point grid, or from a cheap
	to an expensive exchange-correlation functional.		to an expensive exchange-correlation functional.
	To set the number of cores in the first image the tag {{TAG\|NCORE_IN_IMAGE1}} has to be set. The second image then		To set the number of cores in the first image the tag {{TAG\|NCORE_IN_IMAGE1}} has to be set. The second image then
	contains the remaining cores.		contains the remaining cores.}}

	The usage of this tag is also explained in the supplementary information of reference {{cite\|dorner:PRL:2018}}.		The usage of this tag is also explained in the supplementary information of reference {{cite\|dorner:PRL:2018}}.

Karsai at 14:06, 16 October 2024

2024-10-16T14:06:43Z

← Older revision		Revision as of 14:06, 16 October 2024
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	----		----

	[[Category:INCAR tag~~]][[Category:Molecular dynamics~~]][[Category:Advanced molecular-dynamics sampling~~]][[Category:Thermodynamic integration~~]]		[[Category:INCAR tag]][[Category:Advanced molecular-dynamics sampling]]

Karsai at 09:37, 15 October 2024

2024-10-15T09:37:16Z

← Older revision		Revision as of 09:37, 15 October 2024
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	----		----

	[[Category:INCAR tag]][[Category:Molecular dynamics]][[Category:Thermodynamic integration]]		[[Category:INCAR tag]][[Category:Molecular dynamics]][[Category:Advanced molecular-dynamics sampling]][[Category:Thermodynamic integration]]

Jona: mentioning the stress tensor is also averaged after 6.4.3 release

2024-04-29T10:30:10Z

mentioning the stress tensor is also averaged after 6.4.3 release

← Older revision		Revision as of 10:30, 29 April 2024
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	The two VASP calculations are essentially performed independently in subdirectories 01 and 02.		The two VASP calculations are essentially performed independently in subdirectories 01 and 02.
	~~Only the~~ forces and ~~energies~~ of the two calculations are averaged according to the tag {{TAG\|VCAIMAGES}}.		The forces, energies and the stress tensor of the two calculations are averaged according to the tag {{TAG\|VCAIMAGES}}.
	Specifically, the value supplied in the tag {{TAG\|VCAIMAGES}} determines the weight of the calculations		Specifically, the value supplied in the tag {{TAG\|VCAIMAGES}} determines the weight of the calculations
	performed in subdirectory 01. The weight of the second image is 1-{{TAG\|VCAIMAGES}}. The averaging		performed in subdirectory 01. The weight of the second image is 1-{{TAG\|VCAIMAGES}}. The averaging

Schlipf at 15:05, 19 July 2022

2022-07-19T15:05:41Z

← Older revision		Revision as of 15:05, 19 July 2022
Line 23:		Line 23:
	(in the lines writing the free energy "F="). This makes scanning the {{TAG\|OSZICAR}} file for the		(in the lines writing the free energy "F="). This makes scanning the {{TAG\|OSZICAR}} file for the
	required energies of the individual calculations somewhat awkward.		required energies of the individual calculations somewhat awkward.


	Special handling: In some cases it might be desirable to use a different number of cores for		Special handling: In some cases it might be desirable to use a different number of cores for

Schlipf at 15:02, 19 July 2022

2022-07-19T15:02:36Z

← Older revision		Revision as of 15:02, 19 July 2022
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	{{TAGDEF\|VCAIMAGES\|[real]\|-1}}		{{TAGDEF\|VCAIMAGES\|[real]\|-1}}

	Description: The tag {{TAG\|VCAIMAGES}} allows to perform thermodynamic coupling constant integrations. To ~~achive~~ this two molecular dynamics simulations are performed with e.g. different {{TAG\|POTCAR}} or {{TAG\|KPOINTS}} files or different exchange-correlation functionals and force averaging between the two calculations is done{{cite\|dorner:PRL:2018}}.		Description: The tag {{TAG\|VCAIMAGES}} allows to perform thermodynamic coupling constant integrations. To achieve this, two molecular dynamics simulations are performed with e.g. different {{TAG\|POTCAR}} or {{TAG\|KPOINTS}} files or different exchange-correlation functionals, and force averaging between the two calculations is done{{cite\|dorner:PRL:2018}}.
	----		----
	The tag {{TAG\|VCAIMAGES}} internally splits the available nodes into two groups, and each group		The tag {{TAG\|VCAIMAGES}} internally splits the available nodes into two groups, and each group
Line 8:		Line 8:
	the nudged elastic band method described under the tag {{TAG\|IMAGES}}. As opposed to the nudged		the nudged elastic band method described under the tag {{TAG\|IMAGES}}. As opposed to the nudged
	elastic band method, VASP creates always two images by setting the tag {{TAG\|IMAGES}}=2 internally.		elastic band method, VASP creates always two images by setting the tag {{TAG\|IMAGES}}=2 internally.
	The two calculations are performed in ~~the~~ subdirectories 01 and 02 (as opposed to the nudged elastic		The two calculations are performed in subdirectories 01 and 02 (as opposed to the nudged elastic
	band method, ~~the~~ subdirectories 00 and 03 are not required). A precise description of the file		band method, subdirectories 00 and 03 are not required). A precise description of the file
	reading and writing is given below.		reading and writing is given below.

	The two VASP calculations are essentially performed independently in ~~the~~ subdirectories 01 and 02.		The two VASP calculations are essentially performed independently in subdirectories 01 and 02.
	Only the forces and energies of the two calculations are averaged according to the tag {{TAG\|VCAIMAGES}}.		Only the forces and energies of the two calculations are averaged according to the tag {{TAG\|VCAIMAGES}}.
	~~Specificially~~, the value supplied in the tag {{TAG\|VCAIMAGES}} determines the weight of the calculations		Specifically, the value supplied in the tag {{TAG\|VCAIMAGES}} determines the weight of the calculations
	performed in ~~the~~ subdirectory 01. The weight of the second image is 1-{{TAG\|VCAIMAGES}}. The averaging		performed in subdirectory 01. The weight of the second image is 1-{{TAG\|VCAIMAGES}}. The averaging
	is performed after self-consistency has been reached and affects the final total energy as well as		is performed after self-consistency has been reached and affects the final total energy as well as
	the forces. Since the energies and forces are averaged, the trajectories generated by the two simulations		the forces. Since the energies and forces are averaged, the trajectories generated by the two simulations
Line 22:		Line 22:
	"ENERGY OF THE ELECTRON-ION-THERMOSTAT SYSTEM (eV)", as well as in the file {{TAG\|OSZICAR}}		"ENERGY OF THE ELECTRON-ION-THERMOSTAT SYSTEM (eV)", as well as in the file {{TAG\|OSZICAR}}
	(in the lines writing the free energy "F="). This makes scanning the {{TAG\|OSZICAR}} file for the		(in the lines writing the free energy "F="). This makes scanning the {{TAG\|OSZICAR}} file for the
	required energies of the individual calculations somewhat ~~akward.~~		required energies of the individual calculations somewhat awkward.


	~~File handling: When VASP is started it reads the file {{TAG\|INCAR}} in the root directory.~~
	~~The following tags are also read from the root {{TAG\|INCAR}} file:~~
	~~{{TAG\|NCORE_IN_IMAGE1}}, {{TAG\|IMAGES}}, {{TAG\|KIMAGES}}, {{TAG\|FOURORBIT}}, {{TAG\|KPAR}}, {{TAG\|NCORE}},~~
	~~{{TAG\|NCORES_PER_BAND}}, {{TAG\|NPAR}}, {{TAG\|NCSHMEM}}. Subsequently, VASP~~
	~~splits the MPI communicator into two subgroups and continues reading from the {{TAG\|INCAR}}~~
	~~file in the subdirectories 01 and 02. If the INCAR files are not present in the subdirectories 01 or 02,~~
	~~VASP will continue reading from the root INCAR file. The same logic is used from the files {{TAG\|KPOINTS}} and {{TAG\|POTCAR}}:~~
	~~if they exist in the subdirectories, they will be read from the subdirectories 01 and 02; if they~~
	~~are missing, the files are read from the root directory. The {{TAG\|POSCAR}} and all other input files~~
	~~are always read from the subdirectories 01 and 02. All output files (including {{TAG\|OUTCAR}} and {{TAG\|OSZICAR}})~~
	~~are always written to the subdirectories 01 and 02~~.


	Special handling: In some cases it might be desirable to use a different number of cores for		Special handling: In some cases it might be desirable to use a different number of cores for
	the first image and the second image. For instance, this might be expedient for calculations		the first image and the second image. For instance, this might be expedient for calculations
	where ~~thermodynmic~~ integration is performed from a coarse to a dense k-point grid, or from a cheap		where thermodynamic integration is performed from a coarse to a dense k-point grid, or from a cheap
	to an expensive exchange-correlation functional.		to an expensive exchange-correlation functional.
	To set the number of cores in the first image the tag {{TAG\|NCORE_IN_IMAGE1}} has to be set. The second image then		To set the number of cores in the first image the tag {{TAG\|NCORE_IN_IMAGE1}} has to be set. The second image then

Huebsch at 14:38, 7 April 2022

2022-04-07T14:38:49Z

← Older revision		Revision as of 14:38, 7 April 2022
Line 47:		Line 47:
	The usage of this tag is also explained in the supplementary information of reference {{cite\|dorner:PRL:2018}}.		The usage of this tag is also explained in the supplementary information of reference {{cite\|dorner:PRL:2018}}.

	== Related ~~Tags~~ and ~~Sections~~ ==		== Related tags and articles ==
	{{TAG\| NCORE_IN_IMAGE1}}, {{TAG\|SCALEE}}, {{TAG\| IMAGES}}		{{TAG\| NCORE_IN_IMAGE1}}, {{TAG\|SCALEE}}, {{TAG\| IMAGES}}

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	----		----

	[[Category:INCAR]][[Category:Molecular ~~Dynamics~~]][[Category:Thermodynamic integration]]		[[Category:INCAR tag]][[Category:Molecular dynamics]][[Category:Thermodynamic integration]]