Supercell core-hole calculations - Revision history

Csheldon: /* Calculation */

2025-05-12T09:50:11Z

Calculation

← Older revision		Revision as of 09:50, 12 May 2025
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	Run a SCH calculation using for several different super cells, increasing until convergence is achieved.		Run a SCH calculation using for several different super cells, increasing until convergence is achieved.

	{{NB\|mind\|By default, the '''XCH method''' is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}{{=}}2 is selected. XCH places the electron in the lowest conduction band.		{{NB\|mind\|By default, the '''XCH method''' is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}{{=}}2 is selected. XCH places the electron in the lowest conduction band.

Csheldon: /* Calculation */

2025-05-12T09:50:03Z

Calculation

← Older revision		Revision as of 09:50, 12 May 2025
Line 44:		Line 44:

	Run a SCH calculation using for several different super cells, increasing until convergence is achieved.		Run a SCH calculation using for several different super cells, increasing until convergence is achieved.

			{{NB\|mind\|By default, the '''XCH method''' is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}{{=}}2 is selected. XCH places the electron in the lowest conduction band.

			To run an '''FCH calculation''' the setup is completely analogous to an XCH calculation except the number of electrons {{TAG\|NELECT}} needs to be decreased by {{TAG\|CLZ}} (or set to the value as it was used without {{TAG\|ICORELEVEL}}{{=}}2). Then VASP automatically puts a negative background charge to compensate for the missing negative charge.}}

	'''Step 5.''' Compare to experiment		'''Step 5.''' Compare to experiment

	If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the calculated spectra to compare with experiment.		If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the calculated spectra to compare with experiment.

	{{NB\|mind\|By default, the '''XCH method''' is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}{{=}}2 is selected. XCH places the electron in the lowest conduction band.

	To run an '''FCH calculation''' the setup is completely analogous to an XCH calculation except the number of electrons {{TAG\|NELECT}} needs to be decreased by {{TAG\|CLZ}} (or set to the value as it was used without {{TAG\|ICORELEVEL}}{{=}}2). Then VASP automatically puts a negative background charge to compensate for the missing negative charge.}}

	== INCAR tags ==		== INCAR tags ==

Csheldon: /* Treatment of excited electron */

2025-05-12T09:49:39Z

Treatment of excited electron

← Older revision		Revision as of 09:49, 12 May 2025
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	If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the calculated spectra to compare with experiment.		If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the calculated spectra to compare with experiment.

	~~=== Treatment of excited electron ===~~		{{NB\|mind\|By default, the '''XCH method''' is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}{{=}}2 is selected. XCH places the electron in the lowest conduction band.
	{{NB\|mind\|By default, the '''XCH method''' is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}=2 is selected.

	To run an '''FCH calculation''' the setup is completely analogous to an XCH calculation except the number of electrons {{TAG\|NELECT}} needs to be decreased by {{TAG\|CLZ}} (or set to the value as it was used without {{TAG\|ICORELEVEL}}=2). Then VASP automatically puts a negative background charge to compensate for the missing negative charge.}}		To run an '''FCH calculation''' the setup is completely analogous to an XCH calculation except the number of electrons {{TAG\|NELECT}} needs to be decreased by {{TAG\|CLZ}} (or set to the value as it was used without {{TAG\|ICORELEVEL}}{{=}}2). Then VASP automatically puts a negative background charge to compensate for the missing negative charge.}}

	== INCAR tags ==		== INCAR tags ==

Csheldon: /* Calculation */

2025-05-12T09:47:50Z

Calculation

← Older revision		Revision as of 09:47, 12 May 2025
Line 45:		Line 45:
	Run a SCH calculation using for several different super cells, increasing until convergence is achieved.		Run a SCH calculation using for several different super cells, increasing until convergence is achieved.

	~~=== Treatment of excited electron ===~~		'''Step 5.''' Compare to experiment

	~~By default~~, ~~the XCH method is selected~~, ~~since VASP automatically increases~~ the ~~number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}=2 is selected~~.		If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the calculated spectra to compare with experiment.

	~~To run an FCH calculation~~ the ~~setup~~ is ~~completely analogous to an XCH calculation except~~ the number of electrons {{TAG\|NELECT}} ~~needs to be decreased~~ by {{TAG\|CLZ}} ~~(or set to the value as it was used without~~ {{TAG\|ICORELEVEL}}=2~~). Then VASP automatically puts a negative background charge to compensate for the missing negative charge~~.		=== Treatment of excited electron ===
			{{NB\|mind\|By default, the '''XCH method''' is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}=2 is selected.

	'''~~Step 5.~~''' ~~Compare~~ to ~~experiment~~		To run an '''FCH calculation''' the setup is completely analogous to an XCH calculation except the number of electrons {{TAG\|NELECT}} needs to be decreased by {{TAG\|CLZ}} (or set to the value as it was used without {{TAG\|ICORELEVEL}}=2). Then VASP automatically puts a negative background charge to compensate for the missing negative charge.}}

	~~If experimental data is available, try comparing~~ to it. ~~The peak maxima are unlikely to align, so you will need~~ to ~~shift~~ the ~~calculated spectra to compare with experiment~~.

	== INCAR tags ==		== INCAR tags ==

Csheldon: /* Calculation */

2025-05-12T09:46:41Z

Calculation

← Older revision		Revision as of 09:46, 12 May 2025
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	'''Step 5.''' Compare to experiment		'''Step 5.''' Compare to experiment

	If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the spectra to compare ~~exactly~~.		If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the calculated spectra to compare with experiment.

	== INCAR tags ==		== INCAR tags ==

Csheldon at 08:44, 12 May 2025

2025-05-12T08:44:58Z

← Older revision		Revision as of 08:44, 12 May 2025
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	In VASP these two steps are all done in a single calculation.		In VASP these two steps are all done in a single calculation.

	'''Step 3.''' Checking calculational parameters in advance		'''Step 3. (optional)''' Checking calculational parameters in advance

	To check calculational paramaters such as e.g. number of bands, number of irreducible k-points, number of electrons, etc. VASP can be run in a dry mode which doesn't do any "actual" calculations but only does the setup up steps:		To check calculational paramaters such as e.g. number of bands, number of irreducible k-points, number of electrons, etc. VASP can be run in a dry mode which doesn't do any "actual" calculations but only does the setup up steps:
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	Run a SCH calculation using for several different super cells, increasing until convergence is achieved.		Run a SCH calculation using for several different super cells, increasing until convergence is achieved.

			=== Treatment of excited electron ===

			By default, the XCH method is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}=2 is selected.

			To run an FCH calculation the setup is completely analogous to an XCH calculation except the number of electrons {{TAG\|NELECT}} needs to be decreased by {{TAG\|CLZ}} (or set to the value as it was used without {{TAG\|ICORELEVEL}}=2). Then VASP automatically puts a negative background charge to compensate for the missing negative charge.

	'''Step 5.''' Compare to experiment		'''Step 5.''' Compare to experiment
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	*{{TAG\|ISMEAR}}: This sets the type of smearing (broadening) in the electronic calculation. Mind that there is also a second broadening when calculating the spectrum, which is currently always of Gaussian form. Both broadenings affect the form of the spectrum.		*{{TAG\|ISMEAR}}: This sets the type of smearing (broadening) in the electronic calculation. Mind that there is also a second broadening when calculating the spectrum, which is currently always of Gaussian form. Both broadenings affect the form of the spectrum.
	*{{TAG\|SIGMA}}: Sets the smearing (broadening) width in eV within the electronic calculation.		*{{TAG\|SIGMA}}: Sets the smearing (broadening) width in eV within the electronic calculation.

	~~=== Treatment of excited electron ===~~

	~~By default, the XCH method is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}=2 is selected.~~

	To run an FCH calculation the setup is completely analogous to an XCH calculation except the number of electrons {{TAG\|NELECT}} needs to be decreased by {{TAG\|CLZ}} (or set to the value as it was used without {{TAG\|ICORELEVEL}}=2). Then VASP automatically puts a negative background charge to compensate for the missing negative charge.

	== Output ==		== Output ==

Csheldon: /* Calculation */

2025-05-12T08:43:34Z

Calculation

← Older revision		Revision as of 08:43, 12 May 2025
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	'''Step 5.''' Compare to experiment		'''Step 5.''' Compare to experiment

	If experimental data is ~~avaiable~~, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the spectra to compare exactly.		If experimental data is available, try comparing to it. The peak maxima are unlikely to align, so you will need to shift the spectra to compare exactly.

	== INCAR tags ==		== INCAR tags ==

Csheldon at 08:43, 12 May 2025

2025-05-12T08:43:16Z

← Older revision		Revision as of 08:43, 12 May 2025
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	The SCH approach{{cite\|karsai:prb:2018}}{{cite\|unzog:prb:2022}} is explained in detail on the following [[Supercell_core-hole_theory\|theory page]]. When the core hole is explicitly introduced in one of the atoms, i.e., a core electron is removed, it is necessary to eliminate the effective interaction of the core hole with its image across the periodic boundary. That requires using a large supercell so that this interaction is negligible. After the self-consistent electronic minimization is converged in the presence of the core hole, the dielectric function is calculated using Fermi's golden rule.		The SCH approach{{cite\|karsai:prb:2018}}{{cite\|unzog:prb:2022}} is explained in detail on the following [[Supercell_core-hole_theory\|theory page]]. When the core hole is explicitly introduced in one of the atoms, i.e., a core electron is removed, it is necessary to eliminate the effective interaction of the core hole with its image across the periodic boundary. That requires using a large supercell so that this interaction is negligible. After the self-consistent electronic minimization is converged in the presence of the core hole, the dielectric function is calculated using Fermi's golden rule.

	~~As described in detail on the [[Supercell core-hole theory\|theory page]], two~~ different approaches can be used to treat the excited electron. The excited electron can be placed into the lowest conduction band in the '''excited electron and core-hole (XCH)'''{{cite\|hetenyi:jcp:2004}} approach, alternatively the excited electron can be accounted for by a negative background charge in the '''full core-hole (FCH)''' {{cite\|Prendergasst:prl:2006}} method.		Two different approaches can be used to treat the excited electron. The excited electron can be placed into the lowest conduction band in the '''excited electron and core-hole (XCH)'''{{cite\|hetenyi:jcp:2004}} approach, alternatively the excited electron can be accounted for by a negative background charge in the '''full core-hole (FCH)''' {{cite\|Prendergasst:prl:2006}} method.

	== Pre-calculation ==		== Pre-calculation ==

Csheldon at 08:43, 12 May 2025

2025-05-12T08:43:03Z

← Older revision		Revision as of 08:43, 12 May 2025
Line 1:		Line 1:
	The SCH approach{{cite\|karsai:prb:2018}}{{cite\|unzog:prb:2022}} is explained in detail on the following [[Supercell_core-hole_theory\|theory page]]. When the core hole is explicitly introduced in one of the atoms, i.e., a core electron is removed, it is necessary to eliminate the effective interaction of the core hole with its image across the periodic boundary. That requires using a large supercell so that this interaction is negligible. After the self-consistent electronic minimization is converged in the presence of the core hole, the dielectric function is calculated using Fermi's golden rule.		The SCH approach{{cite\|karsai:prb:2018}}{{cite\|unzog:prb:2022}} is explained in detail on the following [[Supercell_core-hole_theory\|theory page]]. When the core hole is explicitly introduced in one of the atoms, i.e., a core electron is removed, it is necessary to eliminate the effective interaction of the core hole with its image across the periodic boundary. That requires using a large supercell so that this interaction is negligible. After the self-consistent electronic minimization is converged in the presence of the core hole, the dielectric function is calculated using Fermi's golden rule.

			As described in detail on the [[Supercell core-hole theory\|theory page]], two different approaches can be used to treat the excited electron. The excited electron can be placed into the lowest conduction band in the '''excited electron and core-hole (XCH)'''{{cite\|hetenyi:jcp:2004}} approach, alternatively the excited electron can be accounted for by a negative background charge in the '''full core-hole (FCH)''' {{cite\|Prendergasst:prl:2006}} method.

	== Pre-calculation ==		== Pre-calculation ==

Csheldon: /* Treatment of excited electron */

2025-05-12T08:42:56Z

Treatment of excited electron

← Older revision		Revision as of 08:42, 12 May 2025
Line 84:		Line 84:

	=== Treatment of excited electron ===		=== Treatment of excited electron ===

	As described in detail on the [[Supercell core-hole theory\|theory page]], two different approaches can be used to treat the excited electron. The excited electron can be placed into the lowest conduction band in the '''excited electron and core-hole (XCH)'''{{cite\|hetenyi:jcp:2004}} approach, alternatively the excited electron can be accounted for by a negative background charge in the '''full core-hole (FCH)''' {{cite\|Prendergasst:prl:2006}} method.

	By default, the XCH method is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}=2 is selected.		By default, the XCH method is selected, since VASP automatically increases the number of electrons {{TAG\|NELECT}} by {{TAG\|CLZ}} if {{TAG\|ICORELEVEL}}=2 is selected.