Category:Electronic ground-state properties - Revision history

Schlipf at 13:16, 13 June 2024

2024-06-13T13:16:53Z

← Older revision		Revision as of 13:16, 13 June 2024
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	{{py4vasp\|url=calculation/partial_density/#py4vasp.calculation._partial_density.PartialDensity.to_stm}} provides some functionality to facilitate creating theoretical STM images.		{{py4vasp\|url=calculation/partial_density/#py4vasp.calculation._partial_density.PartialDensity.to_stm}} provides some functionality to facilitate creating theoretical STM images.
	-->		-->

			[[File:work_function.png\|x300px\|Average potential perpendicular to the surface of the system.]]

	During the electronic optimization, VASP also computes the [[:Category:Potential\|total potential]].		During the electronic optimization, VASP also computes the [[:Category:Potential\|total potential]].

Schlipf: /* Properties of orbitals */

2024-06-13T10:35:57Z

Properties of orbitals

← Older revision		Revision as of 10:35, 13 June 2024
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	Counting all orbitals with eigenvalues in a certain energy interval yields the [[:Category:Density of states\|density of states (DOS)]] ({{FILE\|DOSCAR}}).		Counting all orbitals with eigenvalues in a certain energy interval yields the [[:Category:Density of states\|density of states (DOS)]] ({{FILE\|DOSCAR}}).
	Often, looking at the DOS can provide valuable insight into the electronic properties of a material, e.g., an estimate of the electron itinerancy or specific heat. It is, therefore, often the first step to start towards understanding a novel material.		Often, looking at the DOS can provide valuable insight into the electronic properties of a material, e.g., an estimate of the electron itinerancy or specific heat. It is, therefore, often the first step to start towards understanding a novel material.

			[[File:band.jpg\|x300px\|Band structure plot of energy eigenvalues of orbitals]]

	The [[:Category:Band structure\|band structure]] contains even more details about the electronic eigenvalues ({{FILE\|EIGENVAL}}) by resolving them with respect to the Bloch vector '''k'''.		The [[:Category:Band structure\|band structure]] contains even more details about the electronic eigenvalues ({{FILE\|EIGENVAL}}) by resolving them with respect to the Bloch vector '''k'''.

Huebsch at 10:39, 12 June 2024

2024-06-12T10:39:22Z

← Older revision		Revision as of 10:39, 12 June 2024
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	The orbitals and the density reveal important insights into material properties and are often the first step towards analyzing and understanding a material.		The orbitals and the density reveal important insights into material properties and are often the first step towards analyzing and understanding a material.

	An easy way to visualize the properties discussed below is ~~with~~ {{py4vasp}}.		An easy way to visualize the properties discussed below is using {{py4vasp}}.

	== Properties of orbitals ==		== Properties of orbitals ==

Huebsch at 10:38, 12 June 2024

2024-06-12T10:38:20Z

Schlipf: /* Properties of orbitals */

2024-06-12T09:33:05Z

Properties of orbitals

← Older revision		Revision as of 09:33, 12 June 2024
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	== Properties of orbitals ==		== Properties of orbitals ==

	For practical purposes, one is most interested in the energy ~~eigenvalue~~ of the orbitals and their local projections.		For practical purposes, one is most interested in the energy eigenvalues of the orbitals and their local projections.
	Consider first the eigenvalues:		Consider first the eigenvalues:
	Counting all orbitals with eigenvalues in a certain energy interval yields the [[:Category:Density of states\|density of states (DOS)]].		Counting all orbitals with eigenvalues in a certain energy interval yields the [[:Category:Density of states\|density of states (DOS)]].

Schlipf: /* Properties on the grid */

2024-06-12T09:29:07Z

Properties on the grid

← Older revision		Revision as of 09:29, 12 June 2024
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	For this reason, VASP offers the possibility to create [[band-decomposed charge densities]].		For this reason, VASP offers the possibility to create [[band-decomposed charge densities]].
	Selecting a specific band index or '''k''' point can shed light e.g. on the localization of defects.		Selecting a specific band index or '''k''' point can shed light e.g. on the localization of defects.
	~~Use this~~ feature ~~also~~ to ~~compare to experimental scanning-tunneling-microscopy (STM) images.~~		This feature is helpful to compute the charge density in the vicinity of the Fermi energy.
	~~The~~ charge density ~~near the surface~~ in the vicinity of the Fermi energy is a good first approximation.		At a surface, this density is a good first approximation to compare to experimental scanning-tunneling-microscopy (STM) images.
	<!--		<!--
	{{py4vasp\|url=calculation/partial_density/#py4vasp.calculation._partial_density.PartialDensity.to_stm}} provides some functionality to facilitate creating theoretical STM images.		{{py4vasp\|url=calculation/partial_density/#py4vasp.calculation._partial_density.PartialDensity.to_stm}} provides some functionality to facilitate creating theoretical STM images.
	-->		-->

	~~Another quantity computed during~~ the optimization is the [[:Category:Potential\|total potential]].		During the electronic optimization, VASP also computes the [[:Category:Potential\|total potential]].
	If you want to analyze the potential, use the {{TAG\|WRT_POTENTIAL}} tag to select ~~which~~ potential is written to file.		If you want to analyze the potential, use the {{TAG\|WRT_POTENTIAL}} tag to select the potential written to file.
	~~There is also~~ the legacy flag {{TAG\|LVTOT}} ~~when~~ you only need the total potential.		Alternatively, use the legacy flag {{TAG\|LVTOT}} if you only need the total potential.
	A common ~~use case~~ is to inspect planar averages parallel to surface or interfaces.		A common application is to inspect planar averages parallel to surface or interfaces.
	VASP will automatically ~~compute this average~~ depending on the {{TAG\|IDIPOL}} setting.		VASP will compute these averages automatically depending on the {{TAG\|IDIPOL}} setting.
	Compute the difference of the average potential and the Fermi energy to get the [[Computing the work function\|work function]].		Compute the difference of the average potential and the Fermi energy to get the [[Computing the work function\|work function]].


	[[Category:VASP\| Electronic ground-state properties]]		[[Category:VASP\| Electronic ground-state properties]]

Schlipf at 09:08, 12 June 2024

2024-06-12T09:08:32Z

← Older revision		Revision as of 09:08, 12 June 2024
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	At the end of an [[:Category:Electronic minimization\|electronic minimization]], VASP obtained a converged set of orbitals.		At the end of an [[:Category:Electronic minimization\|electronic minimization]], VASP has obtained a converged set of orbitals.
	From the orbitals, we compute the corresponding density via [[k-point integration]].		From the orbitals, we compute the corresponding density via [[k-point integration]].
	The orbitals and the density reveal important insights into material properties and are often the first step towards analyzing and understanding a material.		The orbitals and the density reveal important insights into material properties and are often the first step towards analyzing and understanding a material.

Schlipf at 09:07, 12 June 2024

2024-06-12T09:07:53Z

← Older revision		Revision as of 09:07, 12 June 2024
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	<!--		<!--
	{{py4vasp\|url=calculation/partial_density/#py4vasp.calculation._partial_density.PartialDensity.to_stm}} provides some functionality to facilitate creating theoretical STM images.		{{py4vasp\|url=calculation/partial_density/#py4vasp.calculation._partial_density.PartialDensity.to_stm}} provides some functionality to facilitate creating theoretical STM images.
			-->

	* potential		Another quantity computed during the optimization is the [[:Category:Potential\|total potential]].
	{{TAG\|LVTOT}}{{TAG\|~~WRT_POTENTIAL~~}}[[~~:Category:Potential~~\|~~potential~~]]		If you want to analyze the potential, use the {{TAG\|WRT_POTENTIAL}} tag to select which potential is written to file.
			There is also the legacy flag {{TAG\|LVTOT}} when you only need the total potential.
			A common use case is to inspect planar averages parallel to surface or interfaces.
			VASP will automatically compute this average depending on the {{TAG\|IDIPOL}} setting.
			Compute the difference of the average potential and the Fermi energy to get the [[Computing the work function\|work function]].

	* STM
	~~[[Band-decomposed charge densities]]~~
	~~--!>~~

	[[Category:VASP\| Electronic ground-state properties]]		[[Category:VASP\| Electronic ground-state properties]]

Schlipf at 12:22, 11 June 2024

2024-06-11T12:22:43Z

← Older revision		Revision as of 12:22, 11 June 2024
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	This serves as a good approximation for the magnetic structure of the system.		This serves as a good approximation for the magnetic structure of the system.

			== Properties on the grid ==

			The [[:Category:Charge density\|charge density]] is defined on the FFT grid and results from a sum over bands and '''k''' points of all occupied orbitals.
			For collinear ({{TAG\|ISPIN}}=2) and noncollinear ({{TAG\|LNONCOLLINEAR}}=T) calculations, it contains additionally the magnetization density.
			VASP stores the charge density in the {{FILE\|CHGCAR}} file and can use it to restart a calculation ({{TAG\|ICHARG}}≥10) which is particular relevant for non-self-consistent calculations like band structures.

			Most of the time, the total charge density is not specific enough to get insight into material properties.
			For this reason, VASP offers the possibility to create [[band-decomposed charge densities]].
			Selecting a specific band index or '''k''' point can shed light e.g. on the localization of defects.
			Use this feature also to compare to experimental scanning-tunneling-microscopy (STM) images.
			The charge density near the surface in the vicinity of the Fermi energy is a good first approximation.
	<!--		<!--
			{{py4vasp\|url=calculation/partial_density/#py4vasp.calculation._partial_density.PartialDensity.to_stm}} provides some functionality to facilitate creating theoretical STM images.

	~~== Properties on the grid ==~~		* potential
			{{TAG\|LVTOT}}{{TAG\|WRT_POTENTIAL}}[[:Category:Potential\|potential]]

	* charge density
	* potential
	* STM		* STM
			[[Band-decomposed charge densities]]
	--!>		--!>

	[[Category:VASP\| Electronic ground-state properties]]		[[Category:VASP\| Electronic ground-state properties]]

Schlipf: /* Properties of orbitals */

2024-06-11T11:54:05Z

Properties of orbitals

← Older revision		Revision as of 11:54, 11 June 2024
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	They make it easy to recognize fundamental and direct bandgaps of the material.		They make it easy to recognize fundamental and direct bandgaps of the material.
	Alternatively, VASP reports these to the {{FILE\|OUTCAR}} file with the verbosity controlled by the {{TAG\|BANDGAP}} tag.		Alternatively, VASP reports these to the {{FILE\|OUTCAR}} file with the verbosity controlled by the {{TAG\|BANDGAP}} tag.
	The electronic eigenvalues determine the occupations of each orbital in conjunction with the settings for {{TAG\|ISMEAR}}, {{TAG\|SIGMA}, and {{TAG\|EFERMI}}.		The electronic eigenvalues determine the occupations of each orbital in conjunction with the settings for {{TAG\|ISMEAR}}, {{TAG\|SIGMA}}, and {{TAG\|EFERMI}}.

	Next, we consider the projections of the orbitals which you activate with the {{TAG\|LORBIT}} tag.		Next, we consider the projections of the orbitals which you activate with the {{TAG\|LORBIT}} tag.

← Older revision		Revision as of 10:38, 12 June 2024
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	At the end of an [[:Category:Electronic minimization\|electronic minimization]], VASP has obtained a converged set of orbitals.		At the end of an [[:Category:Electronic minimization\|electronic minimization]], VASP has obtained a converged set of orbitals ({{FILE\|WAVECAR}}).
	~~From~~ the orbitals~~, we compute~~ the corresponding density via [[k-point integration]].		Based on the orbitals also the corresponding density is computed via [[k-point integration]] ({{FILE\|CHGCAR}}).
	The orbitals and the density reveal important insights into material properties and are often the first step towards analyzing and understanding a material.		The orbitals and the density reveal important insights into material properties and are often the first step towards analyzing and understanding a material.

			An easy way to visualize the properties discussed below is with {{py4vasp}}.

	== Properties of orbitals ==		== Properties of orbitals ==
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	For practical purposes, one is most interested in the energy eigenvalues of the orbitals and their local projections.		For practical purposes, one is most interested in the energy eigenvalues of the orbitals and their local projections.
	Consider first the eigenvalues:		Consider first the eigenvalues:
	Counting all orbitals with eigenvalues in a certain energy interval yields the [[:Category:Density of states\|density of states (DOS)]].		Counting all orbitals with eigenvalues in a certain energy interval yields the [[:Category:Density of states\|density of states (DOS)]] ({{FILE\|DOSCAR}}).
	Often looking at the DOS can provide valuable insight into the electronic properties of a material ~~and~~ is therefore often the first step to start towards understanding a novel material.		Often, looking at the DOS can provide valuable insight into the electronic properties of a material, e.g., an estimate of the electron itinerancy or specific heat. It is, therefore, often the first step to start towards understanding a novel material.
	The [[:Category:Band structure\|band structure]] contains even more details about the electronic eigenvalues by resolving them with respect to the ~~Block~~ vector '''k'''.
			The [[:Category:Band structure\|band structure]] contains even more details about the electronic eigenvalues ({{FILE\|EIGENVAL}}) by resolving them with respect to the Bloch vector '''k'''.
	Usually, one uses high-symmetry paths in the Brillouin zone for band structures.		Usually, one uses high-symmetry paths in the Brillouin zone for band structures.
	They make it easy to recognize fundamental and direct bandgaps of the material.		They make it easy to recognize fundamental and direct bandgaps of the material.
	Alternatively, VASP reports ~~these~~ to the {{FILE\|OUTCAR}} file with the verbosity controlled by the {{TAG\|BANDGAP}} tag.		Alternatively, VASP directly reports the bandgaps to the {{FILE\|OUTCAR}} file with the verbosity controlled by the {{TAG\|BANDGAP}} tag.
	The electronic eigenvalues determine the occupations of each orbital in conjunction with the settings for {{TAG\|ISMEAR}}, {{TAG\|SIGMA}}, and {{TAG\|EFERMI}}.		The electronic eigenvalues determine the occupations of each orbital in conjunction with the settings for {{TAG\|ISMEAR}}, {{TAG\|SIGMA}}, and {{TAG\|EFERMI}}.

	Next, we consider the projections of the orbitals ~~which~~ you activate with the {{TAG\|LORBIT}} tag.		Next, we consider the projections of the orbitals that you activate with the {{TAG\|LORBIT}} tag.
	VASP projects each orbital onto functions with defined angular momentum ~~near~~ each ion.		VASP projects each orbital onto functions with defined angular momentum within the [[PAW formalism\|PAW sphere]] of each ion.
	This site projection augments the data produced by DOS and band structure calculations.		This site projection augments the data produced by DOS and band-structure calculations.
	~~An easy way to visualize these projections is with {{py4vasp}}~~.
	In addition, the projections describe how much charge has a particular angular momentum and spin near an ion.		In addition, the projections describe how much charge has a particular angular momentum and spin near an ion.
	This serves as a good approximation for the magnetic structure of the system.		This serves as a good approximation for the magnetic structure of the system.
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	== Properties on the grid ==		== Properties on the grid ==

	The [[:Category:Charge density\|charge density]] is defined on the ~~FFT grid~~ and results from a sum over bands and '''k''' points of all occupied orbitals.		The [[:Category:Charge density\|charge density]] is defined on a real-space grid in the unit cell and results from a sum over bands and '''k''' points of all occupied orbitals. The grid is often called FFT grid because the underlying calculation requires repeatedly switching between real and reciprocal space via FFTs on that grid.
	For ~~collinear~~ ({{TAG\|ISPIN}}=2~~) and noncollinear (~~{{TAG\|LNONCOLLINEAR}}=T) ~~calculations~~, ~~it contains additionally~~ the magnetization ~~density~~.		For magnetic calculations ({{TAG\|ISPIN}}=2 or {{TAG\|LNONCOLLINEAR}}=T), the orbitals and charge density have additional spin indices and include the magnetization.
	VASP stores the charge density in the {{FILE\|CHGCAR}} file and can use it to restart a calculation ({{TAG\|ICHARG}}≥10) which is ~~particular~~ relevant for non-self-consistent calculations like band ~~structures~~.		VASP stores the charge density in the {{FILE\|CHGCAR}} file and can use it to restart a calculation ({{TAG\|ICHARG}}≥10), which is particularly relevant for non-self-consistent calculations like band-structure calculations.

	Most of the time, the total charge density is not specific enough to get insight into material properties.		Most of the time, the total charge density is not specific enough to get insight into material properties.
	For this reason, VASP offers the possibility ~~to create~~ [[band-decomposed charge densities]].		For this reason, VASP offers the possibility of creating [[band-decomposed charge densities]].
	Selecting a specific band index or '''k''' point can shed light e.g. on the localization of defects.		Selecting a specific band index or '''k''' point can shed light, e.g., on the localization of defects.
	This feature is helpful ~~to compute~~ the charge density in the vicinity of the Fermi energy.		This feature is helpful in computing the charge density in the vicinity of the Fermi energy.
	At a surface, this density is a good first approximation to compare to experimental scanning-tunneling-microscopy (STM) images.		At a surface, this density is a good first approximation to compare to experimental scanning-tunneling-microscopy (STM) images.
	<!--		<!--
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	During the electronic optimization, VASP also computes the [[:Category:Potential\|total potential]].		During the electronic optimization, VASP also computes the [[:Category:Potential\|total potential]].
	If you want to analyze the potential, use the {{TAG\|WRT_POTENTIAL}} tag to select the potential written ~~to file~~.		If you want to analyze the potential, use the {{TAG\|WRT_POTENTIAL}} tag to select the potential that should be written.
	Alternatively, use the legacy ~~flag~~ {{TAG\|LVTOT}} if you only need the total potential.		Alternatively, use the legacy tag {{TAG\|LVTOT}} if you only need the total potential.
	A common application is to inspect planar averages parallel to ~~surface~~ or interfaces.		A common application is to inspect planar averages parallel to surfaces or interfaces.
	VASP will compute these averages automatically depending on the {{TAG\|IDIPOL}} setting.		VASP will compute these averages automatically depending on the {{TAG\|IDIPOL}} setting.
	Compute the difference of the average potential and the Fermi energy to get the [[Computing the work function\|work function]].		Compute the difference of the average potential and the Fermi energy to get the [[Computing the work function\|work function]].