VCA - Revision history

Schlipf at 13:44, 7 March 2025

2025-03-07T13:44:29Z

← Older revision		Revision as of 13:44, 7 March 2025
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	[[Category:INCAR tag]][[Category:~~PAW~~]]		[[Category:INCAR tag]][[Category:Projector-augmented-wave method]]

Karsai: /* References */

2022-04-08T14:55:21Z

References

← Older revision		Revision as of 14:55, 8 April 2022
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	[[Category:INCAR]][[Category:PAW]]		[[Category:INCAR tag]][[Category:PAW]]

Karsai: /* Related Tags and Sections */

2022-04-08T14:55:15Z

Related Tags and Sections

← Older revision		Revision as of 14:55, 8 April 2022
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	'''Mind:''' This tag is currently not supported in combination with {{TAG\|IBRION}} = 5-8 for computing second derivatives, Hessian matrices, and phonon frequencies.		'''Mind:''' This tag is currently not supported in combination with {{TAG\|IBRION}} = 5-8 for computing second derivatives, Hessian matrices, and phonon frequencies.

	== Related ~~Tags~~ and ~~Sections~~ ==		== Related tags and articles ==
	{{TAG\|LVCADER}}		{{TAG\|LVCADER}}

Huebsch at 01:01, 10 August 2021

2021-08-10T01:01:21Z

← Older revision		Revision as of 01:01, 10 August 2021
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	Caveats: Unfortunately, results of this kind of VCA calculations are often not very reliable. The problems are even apparent in the original publications {{cite\|bellaiche:prb:2000}}. The		Caveats: Unfortunately, results of this kind of VCA calculations are often not very reliable. The problems are even apparent in the original publications {{cite\|bellaiche:prb:2000}}. The
	key point is that the used PAW potentials need to be constructed so that the pseudo atomic waves are very similar for the potentials that are "mixed" (in the example above, this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore, the local potentials of the two {{TAG\|POTCAR}} files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is often not even approximately observed (instead, the volume is too large at 50 % mixing). The problem is particularly severe if semi-core states are treated as valence states. For instance, for the Ge and Sn alloy, the d electrons had to be treated as core electrons to obtain reasonable results. Any attempts to treat the d electrons as valence states lead to grossly incorrect results.		key point is that the used PAW potentials need to be constructed so that the pseudo atomic waves are very similar for the potentials that are "mixed" (in the example above, this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore, the local potentials of the two {{TAG\|POTCAR}} files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is often not even approximately observed (instead, the volume is too large at 50 % mixing). The problem is particularly severe if semi-core states are treated as valence states. For instance, for the Ge and Sn alloy, the d electrons had to be treated as core electrons to obtain reasonable results. Any attempts to treat the d electrons as valence states lead to grossly incorrect results.

			'''Mind:''' This tag is currently not supported in combination with {{TAG\|IBRION}} = 5-8 for computing second derivatives, Hessian matrices, and phonon frequencies.

	== Related Tags and Sections ==		== Related Tags and Sections ==

Huebsch at 23:27, 6 August 2021

2021-08-06T23:27:06Z

← Older revision		Revision as of 23:27, 6 August 2021
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	----		----
	The tag {{TAG\|VCA}} must be supplied for each atom type or species found in the {{TAG\|POTCAR}} and {{TAG\|POSCAR}} file, respectively.		The tag {{TAG\|VCA}} must be supplied for each atom type or species found in the {{TAG\|POTCAR}} and {{TAG\|POSCAR}} file, respectively.
	It weights the corresponding POTCAR files according to the values given in the {{TAG\|INCAR}} file, with the default ~~obviously~~		It weights the corresponding {{TAG\|POTCAR}} files according to the values given in the {{TAG\|INCAR}} file, with the default
	being 1. For instance, the formal valency found in the POTCAR files is multiplied by the supplied values~~, and likewise~~, the local potential,		being 1. For instance, the formal valency found in the {{TAG\|POTCAR}} files is multiplied by the supplied values. Likewise, the local potential,
	the augmentation charges, and the non-local pseudopotential strength parameters are scaled by the supplied values.		the augmentation charges, and the non-local pseudopotential strength parameters are scaled by the supplied values.

	It is possible to use this flag to perform calculations in the framework of the virtual crystal approximation.		It is possible to use this flag to perform calculations in the framework of the virtual crystal approximation.
	Say you want to simulate Sn doping in a Ge lattice. ~~Using~~ a POTCAR file with a Ge and Sn data set and the following		Say you want to simulate Sn doping in a Ge lattice. This can be achieved using a {{TAG\|POTCAR}} file with a Ge and Sn data set and the following
	POSCAR file~~, this can be achieved~~:		{{TAG\|POSCAR}} file:

	cd:		cd:
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	If {{TAG\|VCA}} is set to		If {{TAG\|VCA}} is set to
	VCA = 0.99 0.01		VCA = 0.99 0.01
	the Ge atoms are weighted with a weight of 0.99, whereas the Sn atoms are weighted by 0.01 (see ~~<ref name="eckhardt2014indirect"/>~~ for an example application).		the Ge atoms are weighted with a weight of 0.99, whereas the Sn atoms are weighted by 0.01 (see {{cite\|eckhardt:prb:2014}} for an example application).
	The implementation in VASP closely follows the methodology suggested by Bellaiche and Vanderbilt~~.<ref name="bellaiche2000VCA"/>~~		The implementation in VASP closely follows the methodology suggested by Bellaiche and Vanderbilt {{cite\|bellaiche:prb:2000}}.

	~~Caveats~~: ~~Unfortunately results of this kind of VCA calculations are often not very reliable~~. ~~The problems are even apparent in the original publications <ref name="bellaiche2000VCA"/>. The~~
	key point is that the used PAW potentials need to be constructed in such a way that the pseudo atomic waves are very similar for the potentials that are "mixed" (in the example above this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore,
	~~the local potentials of the two POTCAR files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is~~
	~~often not even approximately observed (instead the volume is way too large at 50 % mixing). The problem is particularly severe if semi-core states~~
	~~are treated as valence states. For instance, for the Ge and Sn alloy, the d electrons had to be treated as core electrons to obtain reasonable results.~~
	~~Any attempts to treat the d electrons as valence states lead to grossly incorrect results.~~


			Caveats: Unfortunately, results of this kind of VCA calculations are often not very reliable. The problems are even apparent in the original publications {{cite\|bellaiche:prb:2000}}. The
			key point is that the used PAW potentials need to be constructed so that the pseudo atomic waves are very similar for the potentials that are "mixed" (in the example above, this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore, the local potentials of the two {{TAG\|POTCAR}} files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is often not even approximately observed (instead, the volume is too large at 50 % mixing). The problem is particularly severe if semi-core states are treated as valence states. For instance, for the Ge and Sn alloy, the d electrons had to be treated as core electrons to obtain reasonable results. Any attempts to treat the d electrons as valence states lead to grossly incorrect results.

	== Related Tags and Sections ==		== Related Tags and Sections ==
	{{TAG\|LVCADER}}		{{TAG\|LVCADER}}

	== References ==		== References ==
	~~<references>~~
	<ref name="eckhardt2014indirect">[https://doi.org/10.1103/PhysRevB.89.165201 C. Eckhardt , K. Hummer, and G. Kresse,Indirect-to-direct gap transition in strained and unstrained Snx Ge1−x alloys. Phys. Rev. B 89, 165201 (2014).]</ref>
	~~<ref name="bellaiche2000VCA">[https://doi.org/10.1103/PhysRevB.61.7877 L. Bellaiche and D. Vanderbilt, Phys. Rev. B 61, 7877 (2000).]</ref>~~
	~~</references>~~
	~~----~~

	[[Category:INCAR]][[Category:PAW]]		[[Category:INCAR]][[Category:PAW]]

Miranda.henrique at 10:30, 20 January 2021

2021-01-20T10:30:56Z

← Older revision		Revision as of 10:30, 20 January 2021
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	Description: {{TAG\|VCA}} is short for the virtual crystal approximation; the tag allows to "weight" each species found in the POTCAR file.		Description: {{TAG\|VCA}} is short for the virtual crystal approximation; the tag allows to "weight" each species found in the POTCAR file.
	----		----
	The tag {{TAG\|VCA}} must be supplied for each atom type or species found in the {{TAG\|POTCAR}} and {{TAG\|POSCAR}} file, respectively .		The tag {{TAG\|VCA}} must be supplied for each atom type or species found in the {{TAG\|POTCAR}} and {{TAG\|POSCAR}} file, respectively.
	It weights the corresponding POTCAR files according to the values given in the {{TAG\|INCAR}} file, with the default obviously		It weights the corresponding POTCAR files according to the values given in the {{TAG\|INCAR}} file, with the default obviously
	being 1. For instance the formal valency found in the POTCAR files is multiplied by the supplied values, and likewise the local potential,		being 1. For instance, the formal valency found in the POTCAR files is multiplied by the supplied values, and likewise, the local potential,
	the augmentation charges, and the non-local pseudopotential strength parameters are scaled by the supplied values.		the augmentation charges, and the non-local pseudopotential strength parameters are scaled by the supplied values.

Line 30:		Line 30:
	The implementation in VASP closely follows the methodology suggested by Bellaiche and Vanderbilt.<ref name="bellaiche2000VCA"/>		The implementation in VASP closely follows the methodology suggested by Bellaiche and Vanderbilt.<ref name="bellaiche2000VCA"/>

	Caveats: Unfortunately results of this kind of VCA calculations are often not very reliable. The problems are even apparent in the original publications by <ref name="bellaiche2000VCA"/>. The		Caveats: Unfortunately results of this kind of VCA calculations are often not very reliable. The problems are even apparent in the original publications <ref name="bellaiche2000VCA"/>. The
	key point is that the used PAW potentials need to be constructed in such a way that the pseudo atomic waves are very similar for the potentials		key point is that the used PAW potentials need to be constructed in such a way that the pseudo atomic waves are very similar for the potentials that are "mixed" (in the example above this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore,
	that are "mixed" (in the example above this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore,		the local potentials of the two POTCAR files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is
	the local potentials of the two POTCAR files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is		often not even approximately observed (instead the volume is way too large at 50 % mixing). The problem is particularly severe if semi-core states
	often not even approximately observed (instead the volume is way too large at 50 % mixing). The problem is particularly severe, if semi-core states		are treated as valence states. For instance, for the Ge and Sn alloy, the d electrons had to be treated as core electrons to obtain reasonable results.
	are treated as valence states. For instance, for the Ge and Sn alloy the d electrons had to be treated as core electrons to obtain reasonable results.		Any attempts to treat the d electrons as valence states lead to grossly incorrect results.
	Any attempts to ~~tread~~ the d electrons as valence states lead to ~~crossly~~ incorrect results.

Kresse at 12:05, 16 April 2020

2020-04-16T12:05:54Z

← Older revision		Revision as of 12:05, 16 April 2020
Line 35:		Line 35:
	the local potentials of the two POTCAR files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is		the local potentials of the two POTCAR files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is
	often not even approximately observed (instead the volume is way too large at 50 % mixing). The problem is particularly severe, if semi-core states		often not even approximately observed (instead the volume is way too large at 50 % mixing). The problem is particularly severe, if semi-core states
	are treated as valence states. For instance, for Ge and Sn the d electrons ~~need~~ to be treated as core electrons to obtain reasonable results.		are treated as valence states. For instance, for the Ge and Sn alloy the d electrons had to be treated as core electrons to obtain reasonable results.
			Any attempts to tread the d electrons as valence states lead to crossly incorrect results.

Kresse at 12:03, 16 April 2020

2020-04-16T12:03:55Z

Kresse at 11:42, 16 April 2020

2020-04-16T11:42:36Z

← Older revision		Revision as of 11:42, 16 April 2020
Line 3:		Line 3:
	Description: {{TAG\|VCA}} is short for the virtual crystal approximation; the tag allows to "weight" each species found in the POTCAR file.		Description: {{TAG\|VCA}} is short for the virtual crystal approximation; the tag allows to "weight" each species found in the POTCAR file.
	----		----
	The tag {{TAG\|VCA}} ''has'' to be supplied for each atom type or species found in the {{TAG\|POTCAR}} ~~respectively~~ {{TAG\|POSCAR} file.		The tag {{TAG\|VCA}} ''has'' to be supplied for each atom type or species found in the {{TAG\|POTCAR}} {{TAG\|POSCAR}} file, respectively .
	It weights the corresponding POTCAR files according to the values given in the {{TAG\|INCAR}} file, with the default obviously		It weights the corresponding POTCAR files according to the values given in the {{TAG\|INCAR}} file, with the default obviously
	being 1. For instance the formal valency found in the POTCAR files is multiplied by the supplied values, and likewise		being 1. For instance the formal valency found in the POTCAR files is multiplied by the supplied values, and likewise
Line 30:		Line 30:
	The implementation in VASP closely follows the methotology suggested by Bellaiche and Vanderbilt.<ref name="bellaiche2000VCA"/>		The implementation in VASP closely follows the methotology suggested by Bellaiche and Vanderbilt.<ref name="bellaiche2000VCA"/>

	Caveats: Unfortunately results of such VCA calculations are often not very reliable.		Caveats: Unfortunately results of such VCA calculations are often not very reliable, and even apparent in the original publucations by <ref name="bellaiche2000VCA"/>. The
			key point is that the used PAW potentials need to be constructed in such a manner that the pseudo atomic waves are very similar for the potentials
			that are "mixed" (in the example above this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore,
			the local potential needs to be very similar. This means that results for many of the standard potentials are not accurate. For instance, Vegard's law is
			often not even approximately observed (instead the volume is way too large at 50 %). The problem is particularly severe, if semi-core states
			are treated as valence states. For instance, for Ge and Sn the d electrons need to be treated as core electrons to obtain reasonable results.

Kresse at 11:28, 16 April 2020

2020-04-16T11:28:56Z

← Older revision		Revision as of 11:28, 16 April 2020
Line 27:		Line 27:
	If {{TAG\|LVCA}} is set to		If {{TAG\|LVCA}} is set to
	VCA = 0.99 0.01		VCA = 0.99 0.01
	the Ge atoms are weighted with a weight of 0.99, whereas the Sn atoms are weighted by 0.01.		the Ge atoms are weighted with a weight of 0.99, whereas the Sn atoms are weighted by 0.01 (see <ref name="eckhardt2014indirect"/>).
			The implementation in VASP closely follows the methotology suggested by Bellaiche and Vanderbilt.<ref name="bellaiche2000VCA"/>

	Caveats: Unfortunately results of such VCA calculations are often not very reliable.		Caveats: Unfortunately results of such VCA calculations are often not very reliable.
Line 38:		Line 39:
	<references>		<references>
	<ref name="eckhardt2014indirect">[https://doi.org/10.1103/PhysRevB.89.165201 C. Eckhardt , K. Hummer, and G. Kresse,Indirect-to-direct gap transition in strained and unstrained Snx Ge1−x alloys. Phys. Rev. B 89, 165201 (2014).]</ref>		<ref name="eckhardt2014indirect">[https://doi.org/10.1103/PhysRevB.89.165201 C. Eckhardt , K. Hummer, and G. Kresse,Indirect-to-direct gap transition in strained and unstrained Snx Ge1−x alloys. Phys. Rev. B 89, 165201 (2014).]</ref>
			<ref name="bellaiche2000VCA">[https://doi.org/10.1103/PhysRevB.61.7877 L. Bellaiche and D. Vanderbilt, Phys. Rev. B 61, 7877 (2000).]</ref>
	</references>		</references>
	----		----

	[[Category:INCAR]][[Category:PAW]]		[[Category:INCAR]][[Category:PAW]]

← Older revision		Revision as of 12:03, 16 April 2020
Line 3:		Line 3:
	Description: {{TAG\|VCA}} is short for the virtual crystal approximation; the tag allows to "weight" each species found in the POTCAR file.		Description: {{TAG\|VCA}} is short for the virtual crystal approximation; the tag allows to "weight" each species found in the POTCAR file.
	----		----
	The tag {{TAG\|VCA}} ~~''has'' to~~ be supplied for each atom type or species found in the {{TAG\|POTCAR}} {{TAG\|POSCAR}} file, respectively .		The tag {{TAG\|VCA}} must be supplied for each atom type or species found in the {{TAG\|POTCAR}} and {{TAG\|POSCAR}} file, respectively .
	It weights the corresponding POTCAR files according to the values given in the {{TAG\|INCAR}} file, with the default obviously		It weights the corresponding POTCAR files according to the values given in the {{TAG\|INCAR}} file, with the default obviously
	being 1. For instance the formal valency found in the POTCAR files is multiplied by the supplied values, and likewise		being 1. For instance the formal valency found in the POTCAR files is multiplied by the supplied values, and likewise the local potential,
	the augmentation charges, and the non-local pseudopotential ~~strenght paramters~~ are scaled by the ~~supplies~~ values.		the augmentation charges, and the non-local pseudopotential strength parameters are scaled by the supplied values.

	It is possible to use this flag to perform calculations in the framework of the virtual crystal approximation.		It is possible to use this flag to perform calculations in the framework of the virtual crystal approximation.
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	0.25 0.25 0.25		0.25 0.25 0.25

	If {{TAG\|~~LVCA~~}} is set to		If {{TAG\|VCA}} is set to
	VCA = 0.99 0.01		VCA = 0.99 0.01
	the Ge atoms are weighted with a weight of 0.99, whereas the Sn atoms are weighted by 0.01 (see <ref name="eckhardt2014indirect"/>).		the Ge atoms are weighted with a weight of 0.99, whereas the Sn atoms are weighted by 0.01 (see <ref name="eckhardt2014indirect"/> for an example application).
	The implementation in VASP closely follows the ~~methotology~~ suggested by Bellaiche and Vanderbilt.<ref name="bellaiche2000VCA"/>		The implementation in VASP closely follows the methodology suggested by Bellaiche and Vanderbilt.<ref name="bellaiche2000VCA"/>

	Caveats: Unfortunately results of ~~such~~ VCA calculations are often not very reliable~~, and~~ even apparent in the original ~~publucations~~ by <ref name="bellaiche2000VCA"/>. The		Caveats: Unfortunately results of this kind of VCA calculations are often not very reliable. The problems are even apparent in the original publications by <ref name="bellaiche2000VCA"/>. The
	key point is that the used PAW potentials need to be constructed in such a ~~manner~~ that the pseudo atomic waves are very similar for the potentials		key point is that the used PAW potentials need to be constructed in such a way that the pseudo atomic waves are very similar for the potentials
	that are "mixed" (in the example above this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore,		that are "mixed" (in the example above this would be the Ge and Sn potentials). This can be achieved by carefully optimizing the radial cutoffs. Furthermore,
	the local ~~potential needs~~ to be very similar. This means that results for many ~~of the~~ standard potentials are not accurate. For instance, Vegard's law is		the local potentials of the two POTCAR files need to be very similar. This means that results for many standard potentials are not accurate. For instance, Vegard's law is
	often not even approximately observed (instead the volume is way too large at 50 %). The problem is particularly severe, if semi-core states		often not even approximately observed (instead the volume is way too large at 50 % mixing). The problem is particularly severe, if semi-core states
	are treated as valence states. For instance, for Ge and Sn the d electrons need to be treated as core electrons to obtain reasonable results.		are treated as valence states. For instance, for Ge and Sn the d electrons need to be treated as core electrons to obtain reasonable results.