Category:Electron-phonon interactions - Revision history

Karsai: /* Stochastic displacements approach */

2025-06-05T06:57:46Z

Stochastic displacements approach

← Older revision		Revision as of 06:57, 5 June 2025
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	The calculation is done in two to four steps:		The calculation is done in two to four steps:

	=== Step 1: Create special ~~structures~~ ===		=== Step 1: Create special structure(s) ===
	Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo (MC) sampling. To enable electron-phonon interactions from sampling methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also, {{TAG\|IBRION}}=6 has to be selected (the sampling methods are currently only implemented for {{TAG\|IBRION}}=6).		Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo (MC) sampling. To enable electron-phonon interactions from sampling methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also, {{TAG\|IBRION}}=6 has to be selected (the sampling methods are currently only implemented for {{TAG\|IBRION}}=6).

	For a one-shot calculation, set the following three {{TAG\|INCAR}} tags		For a one-shot calculation, set the following three {{TAG\|INCAR}} tags
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	{{TAG\|TEBEG}} sets the target temperature and {{TAGBL\|PHON_NSTRUCT}} sets the number of random structures for the Monte-Carlo sampling.		{{TAG\|TEBEG}} sets the target temperature and {{TAGBL\|PHON_NSTRUCT}} sets the number of random structures for the Monte-Carlo sampling.

	=== Step 2: Calculate observable ~~for~~ special ~~structures~~ ===		=== Step 2: Calculate observable in special structure(s) ===
	Run calculation for the previously created {{TAG\|POSCAR}} files on the desired observable. These calculations can be anything that is suitable for a Monte Carlo sum <math>\langle O(T)\rangle = \frac{1}{n} \sum\limits_{i=1}^{n} O(x_{T}^{\textrm{MC,i}})</math>, for example band gap calculations, absorption spectra calculations, etc.		Run calculation for the previously created {{TAG\|POSCAR}} files on the desired observable. These calculations can be anything that is suitable for a Monte Carlo sum <math>\langle O(T)\rangle = \frac{1}{n} \sum\limits_{i=1}^{n} O(x_{T}^{\textrm{MC,i}})</math>, for example, band gap calculations, absorption spectra calculations, etc.

	=== Step 3 (optional): Calculate observable for pristine structure ===		=== Step 3 (optional): Calculate observable for pristine structure ===

Karsai: /* Step 1: Create special structures */

2025-06-05T06:52:13Z

Step 1: Create special structures

← Older revision		Revision as of 06:52, 5 June 2025
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	=== Step 1: Create special structures ===		=== Step 1: Create special structures ===
	Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also, {{TAG\|IBRION}}=6 has to be selected (the ~~Monte-Carlo (MC) method is~~ currently only implemented for {{TAG\|IBRION}}=6). For a one-shot calculation, set the following three {{TAG\|INCAR}} tags		Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo (MC) sampling. To enable electron-phonon interactions from sampling methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also, {{TAG\|IBRION}}=6 has to be selected (the sampling methods are currently only implemented for {{TAG\|IBRION}}=6).

			For a one-shot calculation, set the following three {{TAG\|INCAR}} tags
	{{TAGBL\|PHON_NSTRUCT}} = 0		{{TAGBL\|PHON_NSTRUCT}} = 0
	{{TAGBL\|PHON_NTLIST}} = 8		{{TAGBL\|PHON_NTLIST}} = 8

Karsai: /* Stochastic displacements approach */

2025-06-05T06:49:49Z

Stochastic displacements approach

← Older revision		Revision as of 06:49, 5 June 2025
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	The stochastic approach allows obtaining the bandgap renormalization and an approximation of the electronic spectral function due to the ionic degrees of freedom under the static approximation using a supercell approach. This has the advantage that it can be easily implemented and used with different levels of theory to describe the electronic states, such as different [[exchange-correlation functionals]] or even the [[:Category:GW\|GW approximation]]. The disadvantage is that the approach does not include time-dependent or dynamical effects of the phonons (static approximation) and, hence, it does not provide transport properties (see [[#Many-body perturbation theory\|perturbative approach]]).		The stochastic approach allows obtaining the bandgap renormalization and an approximation of the electronic spectral function due to the ionic degrees of freedom under the static approximation using a supercell approach. This has the advantage that it can be easily implemented and used with different levels of theory to describe the electronic states, such as different [[exchange-correlation functionals]] or even the [[:Category:GW\|GW approximation]]. The disadvantage is that the approach does not include time-dependent or dynamical effects of the phonons (static approximation) and, hence, it does not provide transport properties (see [[#Many-body perturbation theory\|perturbative approach]]).

	To displace the atoms along a set of random or a single specially chosen direction {{cite\|zacharias:prb:2016}}, this approach requires the knowledge of the [[phonons]] on a supercell. The displacement length is determined by the temperature of the ionic system. The ~~bandgap~~ can be directly obtained by averaging over the set of randomly displaced supercells, or from the aforementioned special displacement pattern.		To displace the atoms along a set of random or a single specially chosen direction {{cite\|zacharias:prb:2016}}, this approach requires the knowledge of the [[phonons]] on a supercell. The displacement length is determined by the temperature of the ionic system. The desired can be directly obtained by averaging over the set of randomly displaced supercells, or from the aforementioned special displacement pattern.
	The calculation is done in two to four steps:		The calculation is done in two to four steps:

Karsai: /* Stochastic displacements approach */

2025-06-05T06:48:25Z

Stochastic displacements approach

← Older revision		Revision as of 06:48, 5 June 2025
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	For a description of how to do the calculations see [[Electron-phonon interactions from Monte-Carlo sampling\|here]].		For a description of how to do the calculations see [[Electron-phonon interactions from Monte-Carlo sampling\|here]].

	The stochastic approach allows obtaining the bandgap renormalization and an approximation of the electronic spectral function due to the ionic degrees of freedom under the static approximation using a supercell approach. This has the advantage that it can be easily implemented and used with different levels of theory to describe the electronic states, such as different [[exchange-correlation functionals]] or even the [[:Category:GW\|GW approximation]]. The disadvantage is that the approach does not include time-dependent or dynamical effects of the phonons (static approximation) and, hence, it does not provide transport properties (see [[#Many-body perturbation theory\|perturbative approach]])~~. Additionally, it is computationally demanding as it requires many supercell calculations~~.		The stochastic approach allows obtaining the bandgap renormalization and an approximation of the electronic spectral function due to the ionic degrees of freedom under the static approximation using a supercell approach. This has the advantage that it can be easily implemented and used with different levels of theory to describe the electronic states, such as different [[exchange-correlation functionals]] or even the [[:Category:GW\|GW approximation]]. The disadvantage is that the approach does not include time-dependent or dynamical effects of the phonons (static approximation) and, hence, it does not provide transport properties (see [[#Many-body perturbation theory\|perturbative approach]]).

	To displace the atoms along a set of random or a single specially chosen direction {{cite\|zacharias:prb:2016}}, this approach requires the knowledge of the [[phonons]] on a supercell. The displacement length is determined by the temperature of the ionic system. The bandgap can be directly obtained by averaging over the set of randomly displaced supercells, or from the aforementioned special displacement pattern.		To displace the atoms along a set of random or a single specially chosen direction {{cite\|zacharias:prb:2016}}, this approach requires the knowledge of the [[phonons]] on a supercell. The displacement length is determined by the temperature of the ionic system. The bandgap can be directly obtained by averaging over the set of randomly displaced supercells, or from the aforementioned special displacement pattern.

Karsai: /* Stochastic displacements approach */

2025-05-16T14:05:21Z

Stochastic displacements approach

← Older revision		Revision as of 14:05, 16 May 2025
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	=== Step 1: Create special structures ===		=== Step 1: Create special structures ===
	Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also {{TAG\|IBRION}}=6 has to be selected (the Monte-Carlo (MC) method is currently only implemented for {{TAG\|IBRION}}=6). For a one-shot calculation set the following three {{TAG\|INCAR}} tags		Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also, {{TAG\|IBRION}}=6 has to be selected (the Monte-Carlo (MC) method is currently only implemented for {{TAG\|IBRION}}=6). For a one-shot calculation, set the following three {{TAG\|INCAR}} tags
	{{TAGBL\|PHON_NSTRUCT}} = 0		{{TAGBL\|PHON_NSTRUCT}} = 0
	{{TAGBL\|PHON_NTLIST}} = 8		{{TAGBL\|PHON_NTLIST}} = 8
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	{{TAG\|PHON_NSTRUCT}}=0 activates the one-shot method. The number of different temperatures and the list of temperatures (in K) are provided using the tags {{TAG\|PHON_NTLIST}} and {{TAG\|PHON_TLIST}}.		{{TAG\|PHON_NSTRUCT}}=0 activates the one-shot method. The number of different temperatures and the list of temperatures (in K) are provided using the tags {{TAG\|PHON_NTLIST}} and {{TAG\|PHON_TLIST}}.

	To run a full Monte-Carlo calculation set the following tags:		To run a full Monte-Carlo calculation, set the following tags:
	{{TAGBL\|TEBEG}} = 0.0		{{TAGBL\|TEBEG}} = 0.0
	{{TAGBL\|PHON_NSTRUCT}} = 100		{{TAGBL\|PHON_NSTRUCT}} = 100
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	=== Step 3 (optional): Calculate observable for pristine structure ===		=== Step 3 (optional): Calculate observable for pristine structure ===
	Calculate the desired observable for the original "pristine" supercell. This step can be necessary when changes of an observable due to electron-phonon ~~interactions is~~ required. An example ~~for~~ such a calculation is the calculation of the band-gap renormalization due to electron-phonon interactions.		Calculate the desired observable for the original "pristine" supercell. This step can be necessary when changes to an observable due to electron-phonon interaction are required. An example of such a calculation is the calculation of the band-gap renormalization due to electron-phonon interactions.

	=== Step 4 (optional): Averaging of observable ===		=== Step 4 (optional): Averaging of observable ===
	If Monte Carlo sampling was used average the results over the number of structures created in step 1 ({{TAG\|PHON_NSTRUCT}}).		If Monte Carlo sampling was used, average the results over the number of structures created in step 1 ({{TAG\|PHON_NSTRUCT}}).

	== Many-body perturbation theory ==		== Many-body perturbation theory ==

Karsai: /* Step 1: Create special structures */

2025-05-16T14:03:51Z

Step 1: Create special structures

← Older revision		Revision as of 14:03, 16 May 2025
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	=== Step 1: Create special structures ===		=== Step 1: Create special structures ===
	Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also {{TAG\|IBRION}}=6 has to be selected (the Monte-Carlo (MC) method is currently only implemented for {{TAG\|IBRION}}=6).		Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also {{TAG\|IBRION}}=6 has to be selected (the Monte-Carlo (MC) method is currently only implemented for {{TAG\|IBRION}}=6). For a one-shot calculation set the following three {{TAG\|INCAR}} tags
			{{TAGBL\|PHON_NSTRUCT}} = 0
			{{TAGBL\|PHON_NTLIST}} = 8
			{{TAGBL\|PHON_TLIST}} = 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
			{{TAG\|PHON_NSTRUCT}}=0 activates the one-shot method. The number of different temperatures and the list of temperatures (in K) are provided using the tags {{TAG\|PHON_NTLIST}} and {{TAG\|PHON_TLIST}}.

			To run a full Monte-Carlo calculation set the following tags:
			{{TAGBL\|TEBEG}} = 0.0
			{{TAGBL\|PHON_NSTRUCT}} = 100
			{{TAG\|TEBEG}} sets the target temperature and {{TAGBL\|PHON_NSTRUCT}} sets the number of random structures for the Monte-Carlo sampling.

	=== Step 2: Calculate observable for special structures ===		=== Step 2: Calculate observable for special structures ===

Karsai: /* Step 1: Create special structures */

2025-05-16T13:58:40Z

Step 1: Create special structures

← Older revision		Revision as of 13:58, 16 May 2025
Line 20:		Line 20:

	=== Step 1: Create special structures ===		=== Step 1: Create special structures ===
	Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also {{TAG\|IBRION}}=6 has to be selected (the Monte-Carlo (MC) method is currently only implemented for {{TAG\|IBRION}}=6). The description of the remaining required {{TAG\|INCAR}} tags for each method is given below. Both methods produce {{TAG\|POSCAR}} files with different distorted Wycoff positions but unchanged Brillouin matrixThe. The ZG configuration method produces one structure for each temperature defined in {{TAG\|PHON_TLIST}}. The files are labeled as		Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also {{TAG\|IBRION}}=6 has to be selected (the Monte-Carlo (MC) method is currently only implemented for {{TAG\|IBRION}}=6).
	~~POSCAR.T=TEMP.~~
	~~The MC sampling code produces many {{TAG\|POSCAR}} files at a given temperature defined by {{TAG\|TEBEG}}. The files are labeled as~~
	~~POSCAR.T=TEBEG.NUMBER~~
	~~where NUMBER runs from 1 to {{TAG\|PHON_NSTRUCT}}~~.

	=== Step 2: Calculate observable for special structures ===		=== Step 2: Calculate observable for special structures ===

Karsai: /* Step 4 (optional) */

2025-05-16T13:48:27Z

Step 4 (optional)

← Older revision		Revision as of 13:48, 16 May 2025
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	Calculate the desired observable for the original "pristine" supercell. This step can be necessary when changes of an observable due to electron-phonon interactions is required. An example for such a calculation is the calculation of the band-gap renormalization due to electron-phonon interactions.		Calculate the desired observable for the original "pristine" supercell. This step can be necessary when changes of an observable due to electron-phonon interactions is required. An example for such a calculation is the calculation of the band-gap renormalization due to electron-phonon interactions.

	=== Step 4 (optional) ===		=== Step 4 (optional): Averaging of observable ===
	If Monte Carlo sampling was used average the results over the number of structures created in step 1 ({{TAG\|PHON_NSTRUCT}}).		If Monte Carlo sampling was used average the results over the number of structures created in step 1 ({{TAG\|PHON_NSTRUCT}}).

Karsai: /* Step 3 (optional) */

2025-05-16T13:48:13Z

Step 3 (optional)

← Older revision		Revision as of 13:48, 16 May 2025
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	Run calculation for the previously created {{TAG\|POSCAR}} files on the desired observable. These calculations can be anything that is suitable for a Monte Carlo sum <math>\langle O(T)\rangle = \frac{1}{n} \sum\limits_{i=1}^{n} O(x_{T}^{\textrm{MC,i}})</math>, for example band gap calculations, absorption spectra calculations, etc.		Run calculation for the previously created {{TAG\|POSCAR}} files on the desired observable. These calculations can be anything that is suitable for a Monte Carlo sum <math>\langle O(T)\rangle = \frac{1}{n} \sum\limits_{i=1}^{n} O(x_{T}^{\textrm{MC,i}})</math>, for example band gap calculations, absorption spectra calculations, etc.

	=== Step 3 (optional) ===		=== Step 3 (optional): Calculate observable for pristine structure ===
	Calculate the desired observable for the original "pristine" supercell. This step can be necessary when changes of an observable due to electron-phonon interactions is required. An example for such a calculation is the calculation of the band-gap renormalization due to electron-phonon interactions.		Calculate the desired observable for the original "pristine" supercell. This step can be necessary when changes of an observable due to electron-phonon interactions is required. An example for such a calculation is the calculation of the band-gap renormalization due to electron-phonon interactions.

	=== Step 4 (optional) ===		=== Step 4 (optional) ===

Karsai: /* Step 2: Calculate observable for special configurations */

2025-05-16T13:48:00Z

Step 2: Calculate observable for special configurations

← Older revision		Revision as of 13:48, 16 May 2025
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	where NUMBER runs from 1 to {{TAG\|PHON_NSTRUCT}}.		where NUMBER runs from 1 to {{TAG\|PHON_NSTRUCT}}.

	=== Step 2: Calculate observable for special ~~configurations~~===		=== Step 2: Calculate observable for special structures ===
	Run calculation for the previously created {{TAG\|POSCAR}} files on the desired observable. These calculations can be anything that is suitable for a Monte Carlo sum <math>\langle O(T)\rangle = \frac{1}{n} \sum\limits_{i=1}^{n} O(x_{T}^{\textrm{MC,i}})</math>, for example band gap calculations, absorption spectra calculations, etc.		Run calculation for the previously created {{TAG\|POSCAR}} files on the desired observable. These calculations can be anything that is suitable for a Monte Carlo sum <math>\langle O(T)\rangle = \frac{1}{n} \sum\limits_{i=1}^{n} O(x_{T}^{\textrm{MC,i}})</math>, for example band gap calculations, absorption spectra calculations, etc.

← Older revision		Revision as of 06:52, 5 June 2025
Line 20:		Line 20:

	=== Step 1: Create special structures ===		=== Step 1: Create special structures ===
	Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo sampling. To enable electron-phonon interactions from MC methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also, {{TAG\|IBRION}}=6 has to be selected (the ~~Monte-Carlo (MC) method is~~ currently only implemented for {{TAG\|IBRION}}=6). For a one-shot calculation, set the following three {{TAG\|INCAR}} tags		Run a single calculation to create the {{TAG\|POSCAR}} file(s) with special positions either belonging to the ZG configuration method or Monte Carlo (MC) sampling. To enable electron-phonon interactions from sampling methods {{TAG\|PHON_LMC}}=''.TRUE.'' has to be set in the {{TAG\|INCAR}} file. Also, {{TAG\|IBRION}}=6 has to be selected (the sampling methods are currently only implemented for {{TAG\|IBRION}}=6).

			For a one-shot calculation, set the following three {{TAG\|INCAR}} tags
	{{TAGBL\|PHON_NSTRUCT}} = 0		{{TAGBL\|PHON_NSTRUCT}} = 0
	{{TAGBL\|PHON_NTLIST}} = 8		{{TAGBL\|PHON_NTLIST}} = 8

← Older revision		Revision as of 06:48, 5 June 2025
Line 14:		Line 14:
	For a description of how to do the calculations see [[Electron-phonon interactions from Monte-Carlo sampling\|here]].		For a description of how to do the calculations see [[Electron-phonon interactions from Monte-Carlo sampling\|here]].

	The stochastic approach allows obtaining the bandgap renormalization and an approximation of the electronic spectral function due to the ionic degrees of freedom under the static approximation using a supercell approach. This has the advantage that it can be easily implemented and used with different levels of theory to describe the electronic states, such as different [[exchange-correlation functionals]] or even the [[:Category:GW\|GW approximation]]. The disadvantage is that the approach does not include time-dependent or dynamical effects of the phonons (static approximation) and, hence, it does not provide transport properties (see [[#Many-body perturbation theory\|perturbative approach]])~~. Additionally, it is computationally demanding as it requires many supercell calculations~~.		The stochastic approach allows obtaining the bandgap renormalization and an approximation of the electronic spectral function due to the ionic degrees of freedom under the static approximation using a supercell approach. This has the advantage that it can be easily implemented and used with different levels of theory to describe the electronic states, such as different [[exchange-correlation functionals]] or even the [[:Category:GW\|GW approximation]]. The disadvantage is that the approach does not include time-dependent or dynamical effects of the phonons (static approximation) and, hence, it does not provide transport properties (see [[#Many-body perturbation theory\|perturbative approach]]).

	To displace the atoms along a set of random or a single specially chosen direction {{cite\|zacharias:prb:2016}}, this approach requires the knowledge of the [[phonons]] on a supercell. The displacement length is determined by the temperature of the ionic system. The bandgap can be directly obtained by averaging over the set of randomly displaced supercells, or from the aforementioned special displacement pattern.		To displace the atoms along a set of random or a single specially chosen direction {{cite\|zacharias:prb:2016}}, this approach requires the knowledge of the [[phonons]] on a supercell. The displacement length is determined by the temperature of the ionic system. The bandgap can be directly obtained by averaging over the set of randomly displaced supercells, or from the aforementioned special displacement pattern.