POSCAR - Revision history

Singraber at 21:11, 17 October 2025

2025-10-17T21:11:10Z

← Older revision		Revision as of 21:11, 17 October 2025
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	*<span style="color:#89ad01">'''Lattice velocities'''</span> - ''(8 lines), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar8" style="display:inline;"></div>		*<span style="color:#89ad01">'''Lattice velocities'''</span> - ''(8 lines), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar8" style="display:inline;"></div>
	**Contains the lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> and their velocities. Lattice velocities occur when in molecular dynamics simulations, lattice vectors are treated as dynamic variables, i.e., are allowed to change over time ({{TAG\|IBRION}}=0 together with {{TAG\|ISIF}}=3), e.g., Nosé-Hoover thermostat. When written to the {{FILE\|CONTCAR}} file the section starts with a line containing the string <code>Lattice velocities and vectors</code>. While reading in the {{FILE\|POSCAR}} file upon restarting only the first character of the line is checked for <code>L</code> or <code>l</code>. The following line specifies the initialization state of the lattice velocities (usually just the integer 1). The next three lines contain the velocities corresponding to the three lattice vectors divided by the time step given via the {{TAG\|POTIM}} tag. The remaining three lines repeat the actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> where multiplication with the scaling factor <math>s</math> has already been taken into account.		**Contains the lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> and their velocities. Lattice velocities occur when in molecular dynamics simulations, lattice vectors are treated as dynamic variables, i.e., are allowed to change over time ({{TAG\|IBRION}}=0 together with {{TAG\|ISIF}}=3), e.g., [[Nosé-Hoover thermostat]]. When written to the {{FILE\|CONTCAR}} file the section starts with a line containing the string <code>Lattice velocities and vectors</code>. While reading in the {{FILE\|POSCAR}} file upon restarting only the first character of the line is checked for <code>L</code> or <code>l</code>. The following line specifies the initialization state of the lattice velocities (usually just the integer 1). The next three lines contain the velocities corresponding to the three lattice vectors divided by the time step given via the {{TAG\|POTIM}} tag. The remaining three lines repeat the actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> where multiplication with the scaling factor <math>s</math> has already been taken into account.
	<!--		<!--
	*Empty spheres - ''(2 lines + #number of desired empty spheres), optional''		*Empty spheres - ''(2 lines + #number of desired empty spheres), optional''
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	*<span style="color:#424242">'''MD extra'''</span> - ''(variable line number), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar10" style="display:inline;"></div>		*<span style="color:#424242">'''MD extra'''</span> - ''(variable line number), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar10" style="display:inline;"></div>
	**The predictor-corrector coordinates are only provided to continue a molecular dynamics run from a {{TAG\|CONTCAR}} file of a previous run, they cannot be entered by hand. There is first a blank line after the ion velocities, the second line is the initialization state of the predictor-corrector coordinates, and the third line is the time step in MD {{TAG\|POTIM}}. The fourth line is the [[~~Nose-Hoover thermostat\|~~Nosé-Hoover thermostat]] for the (''n'')th and (''n+1'')th iteration (<math>s_{n+1}, \dot{s}_{n+1}, \dot{s}_{n}, s_n</math>). Finally, the predictor-corrector coordinates are printed.		**The predictor-corrector coordinates are only provided to continue a molecular dynamics run from a {{TAG\|CONTCAR}} file of a previous run, they cannot be entered by hand. There is first a blank line after the ion velocities, the second line is the initialization state of the predictor-corrector coordinates, and the third line is the time step in MD {{TAG\|POTIM}}. The fourth line is the [[Nosé-Hoover thermostat]] for the (''n'')th and (''n+1'')th iteration (<math>s_{n+1}, \dot{s}_{n+1}, \dot{s}_{n}, s_n</math>). Finally, the predictor-corrector coordinates are printed.

	<sup>1</sup> "from {{TAG\|CONTCAR}} only": This section is usually not entered manually by the user. It appears in the {{FILE\|CONTCAR}} file output at the end of {{VASP}} runs which involve ionic steps and is intended for restarting a previous calculation.		<sup>1</sup> "from {{TAG\|CONTCAR}} only": This section is usually not entered manually by the user. It appears in the {{FILE\|CONTCAR}} file output at the end of {{VASP}} runs which involve ionic steps and is intended for restarting a previous calculation.

Csheldon at 11:58, 3 June 2025

2025-06-03T11:58:22Z

← Older revision		Revision as of 11:58, 3 June 2025
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	The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.		The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.

	Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], [https://www.ovito.org/ ~~Ovito~~], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).		Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], [https://www.ovito.org/ OVITO], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).
	<!--		<!--
	It is also possible to visualize {{FILE\|POSCAR}} files using {{py4vasp}} as of 10.X:		It is also possible to visualize {{FILE\|POSCAR}} files using {{py4vasp}} as of 10.X:

Csheldon at 11:57, 3 June 2025

2025-06-03T11:57:56Z

← Older revision		Revision as of 11:57, 3 June 2025
Line 1:		Line 1:
	The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.		The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.

	Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).		Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], [https://www.ovito.org/ Ovito], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).
	<!--		<!--
	It is also possible to visualize {{FILE\|POSCAR}} files using {{py4vasp}} as of 10.X:		It is also possible to visualize {{FILE\|POSCAR}} files using {{py4vasp}} as of 10.X:

Csheldon at 07:41, 30 May 2025

2025-05-30T07:41:24Z

← Older revision		Revision as of 07:41, 30 May 2025
Line 1:		Line 1:
	The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.		The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.

	Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).		Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).
			<!--
			It is also possible to visualize {{FILE\|POSCAR}} files using {{py4vasp}} as of 10.X:

			<syntaxhighlight lang="python">
			import py4vasp
			calc = py4vasp.calculation.structure.plot("POSCAR")
			</syntaxhighlight>-->

	==Basic introduction (minimal example)==		==Basic introduction (minimal example)==

Csheldon: /* Full format specification */

2025-05-28T13:51:53Z

Full format specification

Csheldon at 13:43, 28 May 2025

2025-05-28T13:43:47Z

← Older revision		Revision as of 13:43, 28 May 2025
Line 3:		Line 3:
	Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).		Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).

	==~~Minimal~~ example==		==Basic introduction (minimal example)==

	In its simplest form the {{FILE\|POSCAR}} file contains basic information about the lattice, per-species number of ions and their positions. This is sufficient in most situation where a {{VASP}} calculation is started from scratch. Have a look at this example for cubic boron nitride:		In its simplest form the {{FILE\|POSCAR}} file contains basic information about the lattice, per-species number of ions and their positions. This is sufficient in most situation where a {{VASP}} calculation is started from scratch. Have a look at this example for cubic boron nitride:

Csheldon at 13:33, 28 May 2025

2025-05-28T13:33:13Z

← Older revision		Revision as of 13:33, 28 May 2025
Line 1:		Line 1:
	The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.		The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.

	Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA] and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).		Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA], [https://jmol.sourceforge.net/ Jmol], and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).

	==Minimal example==		==Minimal example==

Csheldon at 13:00, 28 May 2025

2025-05-28T13:00:41Z

← Older revision		Revision as of 13:00, 28 May 2025
Line 1:		Line 1:
	The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.		The {{FILE\|POSCAR}} file is a mandatory {{VASP}} input file. It is a plain text file and contains at least the lattice geometry and the ionic positions. Optionally, also starting velocities for a [[:Category:Molecular Dynamics\|molecular-dynamics]] simulation can be provided here. This file shares its format with {{VASP}} output file {{FILE\|CONTCAR}}. That may contain an additional section with predictor-corrector coordinates necessary for restarting [[:Category:Molecular Dynamics\|molecular-dynamics]] runs.

	Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format.		Creating a {{FILE\|POSCAR}} file is often the starting point of {{VASP}}-supported research. It can be written manually or obtained from various online materials and crystallographic databases providing a download in the {{FILE\|POSCAR}} file format. {{FILE\|POSCAR}} files can be visualized using a variety of softwares, including [https://jp-minerals.org/vesta/en/ VESTA] and the [https://wiki.fysik.dtu.dk/ase//gettingstarted/gettingstarted.html Atomic Simulation Environment] (ASE).

	~~==File format==~~		==Minimal example==

	===Minimal example===

	In its simplest form the {{FILE\|POSCAR}} file contains basic information about the lattice, per-species number of ions and their positions. This is sufficient in most situation where a {{VASP}} calculation is started from scratch. Have a look at this example for cubic boron nitride:		In its simplest form the {{FILE\|POSCAR}} file contains basic information about the lattice, per-species number of ions and their positions. This is sufficient in most situation where a {{VASP}} calculation is started from scratch. Have a look at this example for cubic boron nitride:
Line 45:		Line 43:
	The total number of lines with positions must match the total number of ions given in the previous section. The ion species are also derived from there, i.e. in the example above it is implied that the list of positions contains one boron ion, followed by one nitrogen nuclei.		The total number of lines with positions must match the total number of ions given in the previous section. The ion species are also derived from there, i.e. in the example above it is implied that the list of positions contains one boron ion, followed by one nitrogen nuclei.

	===Full format specification===		==Full format specification==

	The {{FILE\|POSCAR}} file format is constructed from multiple sections arranged in a predefined order. Some sections contain only a single line, others span over many lines, some may even be omitted. The following list defines the section order and their contents:		The {{FILE\|POSCAR}} file format is constructed from multiple sections arranged in a predefined order. Some sections contain only a single line, others span over many lines, some may even be omitted. The following list defines the section order and their contents:
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	<sup>1</sup> "from {{TAG\|CONTCAR}} only": This section is usually not entered manually by the user. It appears in the {{FILE\|CONTCAR}} file output at the end of {{VASP}} runs which involve ionic steps and is intended for restarting a previous calculation.		<sup>1</sup> "from {{TAG\|CONTCAR}} only": This section is usually not entered manually by the user. It appears in the {{FILE\|CONTCAR}} file output at the end of {{VASP}} runs which involve ionic steps and is intended for restarting a previous calculation.

	===Precision and symmetry===		==Precision and symmetry==

	VASP determines the symmetry of the system from the {{FILE\| POSCAR}} file.		VASP determines the symmetry of the system from the {{FILE\| POSCAR}} file.

Csheldon: /* Full format specification */

2025-05-28T11:52:28Z

Full format specification

← Older revision		Revision as of 11:52, 28 May 2025
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	::If no initial velocities are provided, the file may end here.		::If no initial velocities are provided, the file may end here.

	*'''Lattice velocities''' - ''(8 lines) - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar8" style="display:inline;"></div>		*'''Lattice velocities''' - ''(8 lines), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar8" style="display:inline;"></div>
	**Contains the lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> and their velocities. Lattice velocities occur when in molecular dynamics simulations, lattice vectors are treated as dynamic variables, i.e., are allowed to change over time ({{TAG\|IBRION}}=0 together with {{TAG\|ISIF}}=3), e.g., Nosé-Hoover thermostat. When written to the {{FILE\|CONTCAR}} file the section starts with a line containing the string <code>Lattice velocities and vectors</code>. While reading in the {{FILE\|POSCAR}} file upon restarting only the first character of the line is checked for <code>L</code> or <code>l</code>. The following line specifies the initialization state of the lattice velocities (usually just the integer 1). The next three lines contain the velocities corresponding to the three lattice vectors divided by the time step given via the {{TAG\|POTIM}} tag. The remaining three lines repeat the actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> where multiplication with the scaling factor <math>s</math> has already been taken into account.		**Contains the lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> and their velocities. Lattice velocities occur when in molecular dynamics simulations, lattice vectors are treated as dynamic variables, i.e., are allowed to change over time ({{TAG\|IBRION}}=0 together with {{TAG\|ISIF}}=3), e.g., Nosé-Hoover thermostat. When written to the {{FILE\|CONTCAR}} file the section starts with a line containing the string <code>Lattice velocities and vectors</code>. While reading in the {{FILE\|POSCAR}} file upon restarting only the first character of the line is checked for <code>L</code> or <code>l</code>. The following line specifies the initialization state of the lattice velocities (usually just the integer 1). The next three lines contain the velocities corresponding to the three lattice vectors divided by the time step given via the {{TAG\|POTIM}} tag. The remaining three lines repeat the actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> where multiplication with the scaling factor <math>s</math> has already been taken into account.
	<!--		<!--
Line 100:		Line 100:
	* {{TAG\|IBRION}}{{=}}44: The vectors in this section are interpreted as directions of the unstable mode in the context of the [[Improved Dimer Method]].\|::}}		* {{TAG\|IBRION}}{{=}}44: The vectors in this section are interpreted as directions of the unstable mode in the context of the [[Improved Dimer Method]].\|::}}

	*'''MD extra''' - ''(variable line number), from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar10" style="display:inline;"></div>		*'''MD extra''' - ''(variable line number), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar10" style="display:inline;"></div>
	**The predictor-corrector coordinates are only provided to continue a molecular dynamics run from a {{TAG\|CONTCAR}} file of a previous run, they cannot be entered by hand. There is first a blank line after the ion velocities, the second line is the initialization state of the predictor-corrector coordinates, and the third line is the time step in MD {{TAG\|POTIM}}. The fourth line is the [[Nose-Hoover thermostat\|Nosé-Hoover thermostat]] for the (''n'')th and (''n+1'')th iteration (<math>s_{n+1}, \dot{s}_{n+1}, \dot{s}_{n}, s_n</math>). Finally, the predictor-corrector coordinates are printed.		**The predictor-corrector coordinates are only provided to continue a molecular dynamics run from a {{TAG\|CONTCAR}} file of a previous run, they cannot be entered by hand. There is first a blank line after the ion velocities, the second line is the initialization state of the predictor-corrector coordinates, and the third line is the time step in MD {{TAG\|POTIM}}. The fourth line is the [[Nose-Hoover thermostat\|Nosé-Hoover thermostat]] for the (''n'')th and (''n+1'')th iteration (<math>s_{n+1}, \dot{s}_{n+1}, \dot{s}_{n}, s_n</math>). Finally, the predictor-corrector coordinates are printed.

Csheldon: /* Full format specification */

2025-05-28T10:34:52Z

Full format specification

Show changes

← Older revision		Revision as of 13:51, 28 May 2025
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	The {{FILE\|POSCAR}} file format is constructed from multiple sections arranged in a predefined order. Some sections contain only a single line, others span over many lines, some may even be omitted. The following list defines the section order and their contents:		The {{FILE\|POSCAR}} file format is constructed from multiple sections arranged in a predefined order. Some sections contain only a single line, others span over many lines, some may even be omitted. The following list defines the section order and their contents:
	[[File:poscar.png\|500px\|thumb\|Layout of {{FILE\|POSCAR}} file.]]		[[File:poscar.png\|500px\|thumb\|Layout of {{FILE\|POSCAR}} file.]]
	* '''Comment''' - ''(1 line), mandatory'' <div id="poscar1" style="display:inline;"></div>		* <span style="color:#424242">'''Comment'''</span> - ''(1 line), mandatory'' <div id="poscar1" style="display:inline;"></div>
	** The first line is reserved for a free user comment, e.g. a system description. The maximum line length is 40 characters, extra characters are truncated.		** The first line is reserved for a free user comment, e.g. a system description. The maximum line length is 40 characters, extra characters are truncated.
	* '''Scaling factor(s)''' - ''(1 line), mandatory'' <div id="poscar2" style="display:inline;"></div>		* <span style="color:#35CABF">'''Scaling factor(s)'''</span> - ''(1 line), mandatory'' <div id="poscar2" style="display:inline;"></div>
	**This line may contain one or three numbers. If one number is provided it specifies a universal lattice scaling factor <math>s</math>. It is multiplied with the three vectors in the following section to obtain the lattice vectors of the unit cell. Also, the ion positions are scaled with this factor if the "Cartesian" mode is selected (see section "Ion positions"). If the number is negative, it is interpreted as the desired cell volume. Then, the scaling factor <math>s</math> is computed automatically to obtain the desired volume. If three numbers are provided in this line they act as individual scaling factors for the x-,y- and z-Cartesian components for the lattice vectors (and "Cartesian" mode ion positions). In this case all three numbers must be positive.		**This line may contain one or three numbers. If one number is provided it specifies a universal lattice scaling factor <math>s</math>. It is multiplied with the three vectors in the following section to obtain the lattice vectors of the unit cell. Also, the ion positions are scaled with this factor if the "Cartesian" mode is selected (see section "Ion positions"). If the number is negative, it is interpreted as the desired cell volume. Then, the scaling factor <math>s</math> is computed automatically to obtain the desired volume. If three numbers are provided in this line they act as individual scaling factors for the x-,y- and z-Cartesian components for the lattice vectors (and "Cartesian" mode ion positions). In this case all three numbers must be positive.
	*'''Lattice''' - ''(3 lines), mandatory'' <div id="poscar3" style="display:inline;"></div>		*<span style="color:#35CABF">'''Lattice'''</span> - ''(3 lines), mandatory'' <div id="poscar3" style="display:inline;"></div>
	**This sections contains three lines defining the lattice vectors. Each line holds the unscaled Cartesian components of one lattice vector. The actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> (in <math>\AA</math>) are the product of the given numbers with the lattice scaling factor <code>s</code>. Set the universal scaling factor to 1 if you want to enter the lattice vectors directly and avoid any additional scaling.		**This sections contains three lines defining the lattice vectors. Each line holds the unscaled Cartesian components of one lattice vector. The actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> (in <math>\AA</math>) are the product of the given numbers with the lattice scaling factor <code>s</code>. Set the universal scaling factor to 1 if you want to enter the lattice vectors directly and avoid any additional scaling.
	*'''Species names''' - ''(1 line), optional'' <div id="poscar4" style="display:inline;"></div>		*<span style="color:#A82C35">'''Species names'''</span> - ''(1 line), optional'' <div id="poscar4" style="display:inline;"></div>
	**This line lists the species of the present ions. The given order should match the order of species appearing in the {{FILE\|POTCAR}} file. This line is optional, if omitted the species names are taken from the {{FILE\|POTCAR}} file. {{NB\|warning\|		**This line lists the species of the present ions. The given order should match the order of species appearing in the {{FILE\|POTCAR}} file. This line is optional, if omitted the species names are taken from the {{FILE\|POTCAR}} file. {{NB\|warning\|
	*In a {{VASP}} calculation the {{FILE\|POTCAR}} file together with the <code>Ions per species</code> section below defines the species of all ions provided in the {{FILE\|POSCAR}} file! This <code>Species names</code> section should be considered only as a helpful comment to identify species when inspecting a {{FILE\|POSCAR}} file independently. Switching species names here will not actually change the species of ions in a calculation if the {{FILE\|POTCAR}} file stays the same!		*In a {{VASP}} calculation the {{FILE\|POTCAR}} file together with the <code>Ions per species</code> section below defines the species of all ions provided in the {{FILE\|POSCAR}} file! This <code>Species names</code> section should be considered only as a helpful comment to identify species when inspecting a {{FILE\|POSCAR}} file independently. Switching species names here will not actually change the species of ions in a calculation if the {{FILE\|POTCAR}} file stays the same!
	*If machine-learned force fields are used ({{TAG\|ML_LMLFF}}{{=}}.TRUE.), it is not possible to give the same name to different groups of atoms in the {{FILE\|POSCAR}} file.		*If machine-learned force fields are used ({{TAG\|ML_LMLFF}}{{=}}.TRUE.), it is not possible to give the same name to different groups of atoms in the {{FILE\|POSCAR}} file.
	*The number of characters a species name can have is only two. If more than two characters are given the code will run but will truncate the name species names after two characters. For example, "Si1" and "Si2" would both be treated as "Si" and "Si". In the case of {{TAG\|ML_LMLFF}}{{=}}.TRUE. the code would be terminated since twice the same name for different species is not allowed.\|::}}		*The number of characters a species name can have is only two. If more than two characters are given the code will run but will truncate the name species names after two characters. For example, "Si1" and "Si2" would both be treated as "Si" and "Si". In the case of {{TAG\|ML_LMLFF}}{{=}}.TRUE. the code would be terminated since twice the same name for different species is not allowed.\|::}}
	*'''Ions per species''' - ''(1 line), mandatory'' <div id="poscar5" style="display:inline;"></div>		*<span style="color:#A82C35">'''Ions per species'''</span> - ''(1 line), mandatory'' <div id="poscar5" style="display:inline;"></div>
	**This mandatory line lists how many ions of each species are present. The given order should match the order of species appearing in the {{FILE\|POTCAR}} file.		**This mandatory line lists how many ions of each species are present. The given order should match the order of species appearing in the {{FILE\|POTCAR}} file.
	*'''Selective dynamics''' - ''(1 line), optional'' <div id="poscar6" style="display:inline;"></div>		*<span style="color:#424242">'''Selective dynamics'''</span> - ''(1 line), optional'' <div id="poscar6" style="display:inline;"></div>
	**If the line after the "Ions per species" section contains <code>Selective dynamics</code> it enables the "selective dynamics" feature (actually only the first character is relevant and must be ''S'' or ''s''). This allows to provide extra flags for each atom signaling whether the respective coordinate(s) of this atom will be allowed to change during the ionic relaxation (or MDs). This setting is useful if only certain shells around a defect or layers near a surface should relax. See also the [[structure optimization]] tips.		**If the line after the "Ions per species" section contains <code>Selective dynamics</code> it enables the "selective dynamics" feature (actually only the first character is relevant and must be ''S'' or ''s''). This allows to provide extra flags for each atom signaling whether the respective coordinate(s) of this atom will be allowed to change during the ionic relaxation (or MDs). This setting is useful if only certain shells around a defect or layers near a surface should relax. See also the [[structure optimization]] tips.
	*'''Ion positions''' - ''(1 line + #atoms), mandatory'' <div id="poscar7" style="display:inline;"></div>		*<span style="color:#3E70EA">'''Ion positions'''</span> - ''(1 line + #atoms), mandatory'' <div id="poscar7" style="display:inline;"></div>
	**Here, the ion positions <math>{\vec R}</math> (in <math>\AA</math>) are listed. The first line selects one of the two possible modes how the coordinates <math>x_1, x_2</math> and <math>x_3</math> given in the following lines are interpreted:		**Here, the ion positions <math>{\vec R}</math> (in <math>\AA</math>) are listed. The first line selects one of the two possible modes how the coordinates <math>x_1, x_2</math> and <math>x_3</math> given in the following lines are interpreted:
	*** "Direct" means the positions are provided in direct (fractional) coordinates:<p><math>{\vec R} = x_1 {\vec a}_1 + x_2 {\vec a}_2 + x_3 {\vec a}_3,</math></p><p>where <math>{\vec R}</math> is the position vector of an ion.</p>		*** "Direct" means the positions are provided in direct (fractional) coordinates:<p><math>{\vec R} = x_1 {\vec a}_1 + x_2 {\vec a}_2 + x_3 {\vec a}_3,</math></p><p>where <math>{\vec R}</math> is the position vector of an ion.</p>
Line 84:		Line 84:
	::If no initial velocities are provided, the file may end here.		::If no initial velocities are provided, the file may end here.

	*'''Lattice velocities''' - ''(8 lines), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar8" style="display:inline;"></div>		*<span style="color:#89ad01">'''Lattice velocities'''</span> - ''(8 lines), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar8" style="display:inline;"></div>
	**Contains the lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> and their velocities. Lattice velocities occur when in molecular dynamics simulations, lattice vectors are treated as dynamic variables, i.e., are allowed to change over time ({{TAG\|IBRION}}=0 together with {{TAG\|ISIF}}=3), e.g., Nosé-Hoover thermostat. When written to the {{FILE\|CONTCAR}} file the section starts with a line containing the string <code>Lattice velocities and vectors</code>. While reading in the {{FILE\|POSCAR}} file upon restarting only the first character of the line is checked for <code>L</code> or <code>l</code>. The following line specifies the initialization state of the lattice velocities (usually just the integer 1). The next three lines contain the velocities corresponding to the three lattice vectors divided by the time step given via the {{TAG\|POTIM}} tag. The remaining three lines repeat the actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> where multiplication with the scaling factor <math>s</math> has already been taken into account.		**Contains the lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> and their velocities. Lattice velocities occur when in molecular dynamics simulations, lattice vectors are treated as dynamic variables, i.e., are allowed to change over time ({{TAG\|IBRION}}=0 together with {{TAG\|ISIF}}=3), e.g., Nosé-Hoover thermostat. When written to the {{FILE\|CONTCAR}} file the section starts with a line containing the string <code>Lattice velocities and vectors</code>. While reading in the {{FILE\|POSCAR}} file upon restarting only the first character of the line is checked for <code>L</code> or <code>l</code>. The following line specifies the initialization state of the lattice velocities (usually just the integer 1). The next three lines contain the velocities corresponding to the three lattice vectors divided by the time step given via the {{TAG\|POTIM}} tag. The remaining three lines repeat the actual lattice vectors <math>{\vec a}_1, {\vec a}_2</math> and <math>{\vec a}_3</math> where multiplication with the scaling factor <math>s</math> has already been taken into account.
	<!--		<!--
Line 90:		Line 90:
	**Note: It seems this feature has never been properly documented and is not used any more.		**Note: It seems this feature has never been properly documented and is not used any more.
	-->		-->
	*'''Ion velocities''' - ''(1 line + #atoms), optional'' <div id="poscar9" style="display:inline;"></div>		*<span style="color:#8342A4">'''Ion velocities'''</span> - ''(1 line + #atoms), optional'' <div id="poscar9" style="display:inline;"></div>
	**Here initial velocities for all ions can be provided. The input format is similar to the section "Ion positions" above. The first line determines the input mode which is either "Direct" or "Cartesian". In contrast to the reading of ion positions, there is no multiplication with the scaling factor <math>s</math> applied in the "Cartesian" mode. Another minor difference is the interpretation of the contents of the first line in this section. In addition to <code>C</code>, <code>c</code>, <code>K</code> or <code>k</code> as the first character also an empty line switches on the "Cartesian" mode. Everything else enables the "Direct" mode instead. The velocity section written out to the {{FILE\|CONTCAR}} file always starts with an empty line and velocities are given in "Cartesian" mode. The following lines contain the velocity vectors of each ion defined in the "Ion positions" section. Velocities must be provided in units "direct lattice vector/timestep" or <math>\AA</math>/fs for "Direct" or "Cartesian" mode, respectively.		**Here initial velocities for all ions can be provided. The input format is similar to the section "Ion positions" above. The first line determines the input mode which is either "Direct" or "Cartesian". In contrast to the reading of ion positions, there is no multiplication with the scaling factor <math>s</math> applied in the "Cartesian" mode. Another minor difference is the interpretation of the contents of the first line in this section. In addition to <code>C</code>, <code>c</code>, <code>K</code> or <code>k</code> as the first character also an empty line switches on the "Cartesian" mode. Everything else enables the "Direct" mode instead. The velocity section written out to the {{FILE\|CONTCAR}} file always starts with an empty line and velocities are given in "Cartesian" mode. The following lines contain the velocity vectors of each ion defined in the "Ion positions" section. Velocities must be provided in units "direct lattice vector/timestep" or <math>\AA</math>/fs for "Direct" or "Cartesian" mode, respectively.
	{{NB\|tip\|Entering velocities by hand is rarely done because a simple alternative to set initial velocities is provided via the {{TAG\|TEBEG}} tag.\|::}}		{{NB\|tip\|Entering velocities by hand is rarely done because a simple alternative to set initial velocities is provided via the {{TAG\|TEBEG}} tag.\|::}}
Line 98:		Line 98:
	* {{TAG\|IBRION}}{{=}}44: The vectors in this section are interpreted as directions of the unstable mode in the context of the [[Improved Dimer Method]].\|::}}		* {{TAG\|IBRION}}{{=}}44: The vectors in this section are interpreted as directions of the unstable mode in the context of the [[Improved Dimer Method]].\|::}}

	*'''MD extra''' - ''(variable line number), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar10" style="display:inline;"></div>		*<span style="color:#424242">'''MD extra'''</span> - ''(variable line number), optional - from {{FILE\|CONTCAR}} only<sup>1</sup>'' <div id="poscar10" style="display:inline;"></div>
	**The predictor-corrector coordinates are only provided to continue a molecular dynamics run from a {{TAG\|CONTCAR}} file of a previous run, they cannot be entered by hand. There is first a blank line after the ion velocities, the second line is the initialization state of the predictor-corrector coordinates, and the third line is the time step in MD {{TAG\|POTIM}}. The fourth line is the [[Nose-Hoover thermostat\|Nosé-Hoover thermostat]] for the (''n'')th and (''n+1'')th iteration (<math>s_{n+1}, \dot{s}_{n+1}, \dot{s}_{n}, s_n</math>). Finally, the predictor-corrector coordinates are printed.		**The predictor-corrector coordinates are only provided to continue a molecular dynamics run from a {{TAG\|CONTCAR}} file of a previous run, they cannot be entered by hand. There is first a blank line after the ion velocities, the second line is the initialization state of the predictor-corrector coordinates, and the third line is the time step in MD {{TAG\|POTIM}}. The fourth line is the [[Nose-Hoover thermostat\|Nosé-Hoover thermostat]] for the (''n'')th and (''n+1'')th iteration (<math>s_{n+1}, \dot{s}_{n+1}, \dot{s}_{n}, s_n</math>). Finally, the predictor-corrector coordinates are printed.