LATTICE CONSTRAINTS - Revision history

Tal at 14:33, 17 February 2025

2025-02-17T14:33:44Z

← Older revision		Revision as of 14:33, 17 February 2025
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	{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}		{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}
	{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.4.3.}}		{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.4.3.}}
			{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|ISIF}}{{=}}4,5 is available from VASP 6.5.1.}}
	{{NB\|warning\| Be aware of a bug in versions < 6.5.0 as described in following forum post[https://www.vasp.at/forum/viewtopic.php?p{{=}}29882#p29882].}}		{{NB\|warning\| Be aware of a bug in versions < 6.5.0 as described in following forum post[https://www.vasp.at/forum/viewtopic.php?p{{=}}29882#p29882].}}

Kaltakm at 13:18, 9 December 2024

2024-12-09T13:18:56Z

← Older revision		Revision as of 13:18, 9 December 2024
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	{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}		{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}
	{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.4.3.}}		{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.4.3.}}
			{{NB\|warning\| Be aware of a bug in versions < 6.5.0 as described in following forum post[https://www.vasp.at/forum/viewtopic.php?p{{=}}29882#p29882].}}

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

Kaltakm at 20:18, 4 December 2024

2024-12-04T20:18:52Z

← Older revision		Revision as of 20:18, 4 December 2024
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	Description: Sets three boolean to selectively allow changes in the lattice vectors.		Description: Sets three boolean to selectively allow changes in the lattice vectors.
	----		----
	The ~~lattice in {{VASP}} is defined by 3~~ lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math>~~, which~~		The lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math>
	~~are~~ defined in the {{FILE\|POSCAR}} file~~. The lattice~~ can be represented by ~~the~~ following matrix:		defined in the {{FILE\|POSCAR}} file can be represented by following matrix:

	<math>		<math>
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	</math>		</math>

	~~The tag~~ {{TAG\|LATTICE_CONSTRAINTS}} ~~can be~~ used to constrain certain entries of this matrix.		{{TAG\|LATTICE_CONSTRAINTS}} is used to constrain certain entries of this matrix during an MD run.
	==Orthorhombic case==		==Orthorhombic case==
	For orthorhombic ~~boxes the lattice~~ <math>\mathbf{A}</math> ~~will be a~~ diagonal ~~matrix of the~~ form:		For orthorhombic unit cells <math>\mathbf{A}</math> is of diagonal form:

	<math>		<math>
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	{{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE.		{{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE.

	~~This way~~, the first two lattice constants are not allowed to change. The third lattice constant needs to be free to allow volume changes for the barostat. The system is then like a piston. The constraints are necessary for liquids in [[NpT ensemble\|NpT]] simulations because if all lattice degrees of freedom are allowed to relax, irreversible deformations of the cell are very likely to happen. This can lead to undesirable results like a very flat supercell, which cannot be used to obtain valid MD trajectories.		Here, the first two lattice constants are not allowed to change. The third lattice constant needs to be free to allow volume changes for the barostat. The system is then like a piston. The constraints are necessary for liquids in [[NpT ensemble\|NpT]] simulations because if all lattice degrees of freedom are allowed to relax, irreversible deformations of the cell are very likely to happen. This can lead to undesirable results like a very flat supercell, which cannot be used to obtain valid MD trajectories.

	For [[Ionic minimization\|structure relaxation]] ({{TAG\|IBRION}}=1,2), {{TAG\|LATTICE_CONSTRAINTS}} is useful to relax the lattice constants of 2D materials. In case of a slab in the <math>\mathbf{a}_1</math>-<math>\mathbf{a}_2</math> plane, add vacuum padding along <math>\mathbf{a}_3</math> and set		For [[Ionic minimization\|structure relaxation]] ({{TAG\|IBRION}}=1,2), {{TAG\|LATTICE_CONSTRAINTS}} is useful to relax the lattice constants of 2D materials. In case of a slab in the <math>\mathbf{a}_1</math>-<math>\mathbf{a}_2</math> plane, add vacuum padding along <math>\mathbf{a}_3</math> and set

Jona at 10:34, 5 February 2024

2024-02-05T10:34:06Z

← Older revision		Revision as of 10:34, 5 February 2024
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	So only the <math>yy</math>/<math>a_{22}</math> entry of the lattice <math>\mathbf{A}</math> will change.		So only the <math>yy</math>/<math>a_{22}</math> entry of the lattice <math>\mathbf{A}</math> will change.
	{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}		{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}
	{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.5.0.}}		{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.4.3.}}

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

Jona: /* Non-orthorhombic case */

2024-02-05T10:02:38Z

Non-orthorhombic case

← Older revision		Revision as of 10:02, 5 February 2024
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	to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.		to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.
	For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .~~FALSE~~. .TRUE. the used stress tensor will look like		For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .TRUE. .TRUE. the used stress tensor will look like

	<math>		<math>
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	and therefore the first row and the first column of the lattice <math>\mathbf{A}</math> will not change.		and therefore the first row and the first column of the lattice <math>\mathbf{A}</math> will not change.
	Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .~~FALSE~~. .~~TRUE~~. resulting in the following		Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .TRUE. .FALSE. resulting in the following
	stress tensor		stress tensor

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	{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}		{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}
	{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.5.0.}}		{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.5.0.}}

	== Related tags and articles ==		== Related tags and articles ==
	{{TAG\|IBRION}}, {{TAG\|MDALGO}}, [[:Category:Interface pinning\|Interface pinning]]		{{TAG\|IBRION}}, {{TAG\|MDALGO}}, [[:Category:Interface pinning\|Interface pinning]]

Jona at 18:09, 31 January 2024

2024-01-31T18:09:13Z

← Older revision		Revision as of 18:09, 31 January 2024
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	to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.		to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.
	For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. the used stress tensor will look like		For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. the used stress tensor will look like

	<math>		<math>
	\mathbf{\sigma} =		\mathbf{\sigma} =
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	\end{bmatrix},		\end{bmatrix},
	</math>		</math>

	and therefore the first row and the first column of the lattice <math>\mathbf{A}</math> will not change.		and therefore the first row and the first column of the lattice <math>\mathbf{A}</math> will not change.
	Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. resulting in the following		Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. resulting in the following

Jona at 17:06, 31 January 2024

2024-01-31T17:06:50Z

← Older revision		Revision as of 17:06, 31 January 2024
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	Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. resulting in the following		Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. resulting in the following
	stress tensor		stress tensor

	<math>		<math>
	\mathbf{\sigma} =		\mathbf{\sigma} =
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	\end{bmatrix}		\end{bmatrix}
	</math>		</math>
	So only the <math>yy</math>/<math>a_{22}<math> entry of the lattice <math>\mathbf{A}</math> will change.
			So only the <math>yy</math>/<math>a_{22}</math> entry of the lattice <math>\mathbf{A}</math> will change.
	{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}		{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}
	{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.5.0.}}		{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.5.0.}}

Jona at 17:06, 31 January 2024

2024-01-31T17:06:08Z

← Older revision		Revision as of 17:06, 31 January 2024
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	0 & zy & zz		0 & zy & zz
	\end{bmatrix},		\end{bmatrix},
	</~~maht~~>		</math>
	and therefore the first row and the first column of the lattice <math>\mathbf{A}</math> will not change.		and therefore the first row and the first column of the lattice <math>\mathbf{A}</math> will not change.
	Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. resulting in the following		Another example would be to set {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. resulting in the following

Jona at 17:05, 31 January 2024

2024-01-31T17:05:34Z

← Older revision		Revision as of 17:05, 31 January 2024
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	==Non-orthorhombic case==		==Non-orthorhombic case==
	For non-orthorhombic boxes {{TAG\|LATTICE_CONSTRAINTS}} is more complicated to use. The tag will set certain rows and columns of the stress tensor		For non-orthorhombic boxes {{TAG\|LATTICE_CONSTRAINTS}} is more complicated to use. The tag will set certain rows and columns of the stress tensor

	<math>		<math>
	\mathbf{\sigma} =		\mathbf{\sigma} =
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	\end{bmatrix},		\end{bmatrix},
	</math>		</math>

	to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.		to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.
	For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. the used stress tensor will look like		For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. the used stress tensor will look like

Jona at 17:05, 31 January 2024

2024-01-31T17:05:04Z

← Older revision		Revision as of 17:05, 31 January 2024
Line 39:		Line 39:
	==Non-orthorhombic case==		==Non-orthorhombic case==
	For non-orthorhombic boxes {{TAG\|LATTICE_CONSTRAINTS}} is more complicated to use. The tag will set certain rows and columns of the stress tensor		For non-orthorhombic boxes {{TAG\|LATTICE_CONSTRAINTS}} is more complicated to use. The tag will set certain rows and columns of the stress tensor
	~~\begin{equation}~~		<math>
	\mathbf{\sigma} =		\mathbf{\sigma} =
	\begin{bmatrix}		\begin{bmatrix}
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	zx & zy & zz		zx & zy & zz
	\end{bmatrix},		\end{bmatrix},
	~~\end{equation}~~		</math>
	to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.		to zero. By setting certain entries of the stress tensor to zero the corresponding entries of the lattice <math>\mathbf{A}</math> will not be updated.
	For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. the used stress tensor will look like		For example when setting {{TAGBL\|LATTICE_CONSTRAINTS}} = .FALSE. .FALSE. .TRUE. the used stress tensor will look like

← Older revision		Revision as of 14:33, 17 February 2025
Line 77:		Line 77:
	{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}		{{NB\|mind\| Note that for non-orthorhombic boxes the angles between the lattice vectors <math>\mathbf{a}_{1}</math>, <math>\mathbf{a}_{2}</math>, <math>\mathbf{a}_{3}</math> will not be conserved.}}
	{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.4.3.}}		{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|IBRION}}{{=}}1,2 is available from VASP 6.4.3.}}
			{{NB\|mind\| {{TAG\|LATTICE_CONSTRAINTS}} in combination with {{TAG\|ISIF}}{{=}}4,5 is available from VASP 6.5.1.}}
	{{NB\|warning\| Be aware of a bug in versions < 6.5.0 as described in following forum post[https://www.vasp.at/forum/viewtopic.php?p{{=}}29882#p29882].}}		{{NB\|warning\| Be aware of a bug in versions < 6.5.0 as described in following forum post[https://www.vasp.at/forum/viewtopic.php?p{{=}}29882#p29882].}}