Electron-phonon accumulators - Revision history

Singraber at 08:10, 24 October 2025

2025-10-24T08:10:54Z

← Older revision		Revision as of 08:10, 24 October 2025
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	Let us look at the following example. If we set		Let us look at the following example. If we set
	* {{~~TAGO~~\|ELPH_SCATTERING_APPROX\|SERTA MRTA_TAU}}		* {{TAG\|ELPH_SCATTERING_APPROX\|SERTA MRTA_TAU}}
	* {{~~TAGO~~\|ELPH_SELFEN_MU\|-0.1 0.0 0.1}}		* {{TAG\|ELPH_SELFEN_MU\|-0.1 0.0 0.1}}
	then it would take a total of 6 calculations to get all combinations of scattering approximations and chemical potentials.		then it would take a total of 6 calculations to get all combinations of scattering approximations and chemical potentials.
	It would be very inefficient to recalculate all the electron-phonon matrix elements for each such combination.		It would be very inefficient to recalculate all the electron-phonon matrix elements for each such combination.

Csheldon: /* Related tags and articles */

2025-10-21T10:38:18Z

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← Older revision		Revision as of 10:38, 21 October 2025
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	* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]		* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]
	* [[Electronic transport coefficients]]		* [[Electronic transport coefficients]]
	* [[Chemical potential]]		* [[Chemical potential in electron-phonon interactions]]
	* {{TAG\|ELPH_SCATTERING_APPROX}}		* {{TAG\|ELPH_SCATTERING_APPROX}}
	* {{TAG\|ELPH_SELFEN_MU}}		* {{TAG\|ELPH_SELFEN_MU}}

Csheldon: /* Related tags and articles */

2025-10-20T14:15:00Z

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← Older revision		Revision as of 14:15, 20 October 2025
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	* [[Bandgap_renormalization_due_to_electron-phonon_coupling\|Band-structure renormalization]]		* [[Bandgap_renormalization_due_to_electron-phonon_coupling\|Band-structure renormalization]]
	* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]		* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]
			* [[Electronic transport coefficients]]
	* [[Chemical potential]]		* [[Chemical potential]]
	* {{TAG\|ELPH_SCATTERING_APPROX}}		* {{TAG\|ELPH_SCATTERING_APPROX}}

Csheldon: /* Related tags and articles */

2025-10-20T13:14:06Z

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← Older revision		Revision as of 13:14, 20 October 2025
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	* {{TAG\|ELPH_SCATTERING_APPROX}}		* {{TAG\|ELPH_SCATTERING_APPROX}}
	* {{TAG\|ELPH_SELFEN_MU}}		* {{TAG\|ELPH_SELFEN_MU}}
			* {{TAG\|ELPH_SELFEN_MU_RANGE}}
	* {{TAG\|ELPH_SELFEN_CARRIER_DEN}}		* {{TAG\|ELPH_SELFEN_CARRIER_DEN}}
			* {{TAG\|ELPH_SELFEN_CARRIER_DEN_RANGE}}
	* {{TAG\|ELPH_SELFEN_CARRIER_PER_CELL}}		* {{TAG\|ELPH_SELFEN_CARRIER_PER_CELL}}
	* {{TAG\|ELPH_MODE}}		* {{TAG\|ELPH_MODE}}

Csheldon at 08:47, 20 October 2025

2025-10-20T08:47:55Z

← Older revision		Revision as of 08:47, 20 October 2025
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	Instead, VASP internally creates an accumulator for each combination of {{TAG\|ELPH_SCATTERING_APPROX}} and {{TAG\|ELPH_SELFEN_MU}}, accumulating the results for all combinations without the need to recompute matrix elements.		Instead, VASP internally creates an accumulator for each combination of {{TAG\|ELPH_SCATTERING_APPROX}} and {{TAG\|ELPH_SELFEN_MU}}, accumulating the results for all combinations without the need to recompute matrix elements.
	This is a much more efficient approach, often with negligible additional computational cost.		This is a much more efficient approach, often with negligible additional computational cost.

	{{NB\|mind\|Different temperatures supplied via {{TAG\|ELPH_SELFEN_TEMPS}} will ''not'' create additional accumulators. The temperatures are handled as an array inside each accumulator.}}		{{NB\|mind\|Different temperatures supplied via {{TAG\|ELPH_SELFEN_TEMPS}} will ''not'' create additional accumulators. The temperatures are handled as an array inside each accumulator.}}

Csheldon: /* Related tags and articles */

2025-10-20T08:47:02Z

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← Older revision		Revision as of 08:47, 20 October 2025
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	* [[Bandgap_renormalization_due_to_electron-phonon_coupling\|Band-structure renormalization]]		* [[Bandgap_renormalization_due_to_electron-phonon_coupling\|Band-structure renormalization]]
	* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]		* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]
			* [[Chemical potential]]
	* {{TAG\|ELPH_SCATTERING_APPROX}}		* {{TAG\|ELPH_SCATTERING_APPROX}}
	* {{TAG\|ELPH_SELFEN_MU}}		* {{TAG\|ELPH_SELFEN_MU}}

Csheldon at 08:45, 20 October 2025

2025-10-20T08:45:23Z

← Older revision		Revision as of 08:45, 20 October 2025
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	Performing electron-phonon calculations using the [[Category:Electron-phonon_interactions#Many-body_perturbation_theory\|perturbative approach]], for example, to compute [[Transport_coefficients_including_electron-phonon_scattering \| transport coefficients]] or the [[Bandgap_renormalization_due_to_electron-phonon_coupling \| renormalization of the electronic band structure]], one of the most expensive task is computing the electron-phonon matrix elements.		Performing electron-phonon calculations using the [[Category:Electron-phonon_interactions#Many-body_perturbation_theory\|perturbative approach]], for example, to compute [[Transport_coefficients_including_electron-phonon_scattering \| transport coefficients]] or the [[Bandgap_renormalization_due_to_electron-phonon_coupling \| renormalization of the electronic band structure]], one of the most expensive task is computing the electron-phonon matrix elements.
	Accumulators provide a mechanism to efficiently reuse computed matrix elements in the electron–phonon module.		Accumulators provide a mechanism to efficiently reuse computed matrix elements in the electron–phonon module.
	It allows to perform a single VASP run while evaluating multiple derived quantities—such as transport coefficients under different scattering approximations or at varying chemical potentials—without recalculating the matrix elements.		It allows to perform a single VASP run while evaluating multiple derived quantities—such as transport coefficients under different scattering approximations or at varying chemical potentials—without recalculating the matrix elements (for more information on the theory of chemical potentials see [[Chemical potential\|chemical potential]]).
	The accumulator technique circumvents the need to repeat these calculations for every set of parameters.		The accumulator technique circumvents the need to repeat these calculations for every set of parameters.

Huebsch at 07:10, 12 May 2025

2025-05-12T07:10:17Z

← Older revision		Revision as of 07:10, 12 May 2025
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	~~When running~~ electron-phonon calculations, for example, to compute [[Transport_coefficients_including_electron-phonon_scattering \| transport coefficients]] or the [[Bandgap_renormalization_due_to_electron-phonon_coupling \| renormalization of the electronic ~~bandstructure~~]]~~, VASP tries to be as efficient as possible.~~		Performing electron-phonon calculations using the [[Category:Electron-phonon_interactions#Many-body_perturbation_theory\|perturbative approach]], for example, to compute [[Transport_coefficients_including_electron-phonon_scattering \| transport coefficients]] or the [[Bandgap_renormalization_due_to_electron-phonon_coupling \| renormalization of the electronic band structure]], one of the most expensive task is computing the electron-phonon matrix elements.
	~~Typically~~, one of the most expensive ~~parts to compute are~~ the electron-phonon matrix elements.
	Accumulators provide a mechanism to efficiently reuse computed matrix elements in the electron–phonon module.		Accumulators provide a mechanism to efficiently reuse computed matrix elements in the electron–phonon module.
	~~This functionality~~ allows ~~you~~ to perform a single VASP run while evaluating multiple derived quantities—such as transport coefficients under different scattering approximations or at varying chemical potentials—without recalculating the matrix elements.		It allows to perform a single VASP run while evaluating multiple derived quantities—such as transport coefficients under different scattering approximations or at varying chemical potentials—without recalculating the matrix elements.
	The accumulator technique circumvents the need to repeat these calculations for every set of parameters.		The accumulator technique circumvents the need to repeat these calculations for every set of parameters.

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	The output of each accumulator is provided in the {{FILE\|OUTCAR}} file as well as in the {{FILE\|vaspout.h5}} file.		The output of each accumulator is provided in the {{FILE\|OUTCAR}} file as well as in the {{FILE\|vaspout.h5}} file.
	In both cases, each accumulator is labeled by a unique ID that ~~simple~~ counts the number of accumulators.		In both cases, each accumulator is labeled by a unique ID that simply counts the number of accumulators.
	In this section, we explain the ~~structure~~ of the output ~~in terms of accumulators.~~		In this section, we explain the format of the output.
	~~This should help you to quickly find the relevant data that was produced by the electron-phonon code~~.

	=== Plain-text output in the {{FILE\|OUTCAR}} file ===		=== Plain-text output in the {{FILE\|OUTCAR}} file ===
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	6 T T T		6 T T T
	</pre>		</pre>
	The difference between the two accumulators is in the scattering approximation: one uses CRTA and one uses SERTA.		The difference between the two accumulators is in the scattering approximation (set by {{TAG\|ELPH_SCATTERING_APPROX}}): one uses CRTA and one uses SERTA.
	{{NB\|mind\|The difference between CRTA and SERTA is only relevant in the context of [[Transport_coefficients_including_electron-phonon_scattering \| transport calculations]]. The computed self-energies do not depend on the scattering approximation.}}		{{NB\|mind\|The difference between CRTA and SERTA is only relevant in the context of [[Transport_coefficients_including_electron-phonon_scattering \| transport calculations]]. The computed self-energies do not depend on the scattering approximation.}}
	This way, you can quickly figure out which accumulator corresponds to which combination of computational parameters.		This way, you can quickly figure out which accumulator corresponds to which combination of computational parameters.
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	The information in each accumulator is also written to the standard {{FILE\|vaspout.h5}} binary output file.		The information in each accumulator is also written to the standard {{FILE\|vaspout.h5}} binary output file.
	In this case, the accumulators are organized as HDF5 groups with the unique accumulator ID being part of the group name.		In this case, the accumulators are organized as HDF5 groups, with the unique accumulator ID being part of the group name.
	This is an example output showing the electron-phonon section of the HDF5 file:		This is an example output showing the electron-phonon section of the HDF5 file:
	<pre class="mw-collapsible">		<pre class="mw-collapsible">
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	;<tt>ncalculators</tt> : total number of accumulators (product of all <tt>id_size</tt> entries)		;<tt>ncalculators</tt> : total number of accumulators (product of all <tt>id_size</tt> entries)

	So for example, if the meta-data output looks like this:		So, for example, if the meta-data output looks like this:
	<pre class="mw-collapsible">		<pre class="mw-collapsible">
	id_name: "selfen_delta ", "nbands_sum ", "selfen_muij ", "selfen_approx "		id_name: "selfen_delta ", "nbands_sum ", "selfen_muij ", "selfen_approx "

Mani: Add HDF5 section

2025-02-28T11:28:46Z

Add HDF5 section

@@ Line 27: / Line 27: @@
 In this section, we explain the structure of the output in terms of accumulators.
 This should help you to quickly find the relevant data that was produced by the electron-phonon code.
 In the {{FILE|OUTCAR}} file, each accumulator is first listed with its ID, <tt>N</tt>, and all the relevant information that defines this accumulator is written in a corresponding block.
 Here is an example output that defines two self-energy accumulators:
-<pre>
+<pre class="mw-collapsible">
 Electron self-energy accumulator N =  1
 ----------------------------------
@@ Line 76: / Line 78: @@
 The computed self-energies for each accumulator are then given below.
 Here is an example output for the first accumulator and the first temperature:
-<pre>
+<pre class="mw-collapsible">
 Electron self-energy accumulator N=  1
   T=       0. K
@@ Line 95: / Line 97: @@
 The corresponding {{FILE|OUTCAR}} output has a structure that is similar to that of the self-energy.
 First, the transport accumulators are listed and defined:
-<pre>
+<pre class="mw-collapsible">
 Transport calculator N =  1
 ----------------------------------
@@ Line 142: / Line 144: @@
 This is then followed by the output of the transport coefficients for each accumulator and each temperature.
 The corresponding example output looks like this:
-<pre>
+<pre class="mw-collapsible">
 Transport for self-energy accumulator N=     1
                   T K               mu eV           sigma S/m      mob cm^2/(V.s)       seebeck μV/K         peltier μV     kappa_e W/(m.K)
@@ Line 156: / Line 158: @@
 </pre>
 This allows us to identify the first data set (<tt>N = 1</tt>) as the CRTA calculation and the second data set (<tt>N = 2</tt>) as the SERTA calculation.
 == Related tags and articles ==

Mani: Change language

2025-02-28T09:23:29Z

Change language

← Older revision		Revision as of 09:23, 28 February 2025
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	Typically, one of the most expensive parts to compute are the electron-phonon matrix elements.		Typically, one of the most expensive parts to compute are the electron-phonon matrix elements.
	Accumulators provide a mechanism to efficiently reuse computed matrix elements in the electron–phonon module.		Accumulators provide a mechanism to efficiently reuse computed matrix elements in the electron–phonon module.
	This functionality allows ~~one~~ to perform a single VASP run while evaluating multiple derived quantities—such as transport coefficients under different scattering approximations or at varying chemical potentials—without recalculating the matrix elements.		This functionality allows you to perform a single VASP run while evaluating multiple derived quantities—such as transport coefficients under different scattering approximations or at varying chemical potentials—without recalculating the matrix elements.
	The accumulator technique circumvents the need to repeat these calculations for every set of parameters.		The accumulator technique circumvents the need to repeat these calculations for every set of parameters.

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	* Multiple chemical potentials set via {{TAG\|ELPH_SELFEN_MU}}.		* Multiple chemical potentials set via {{TAG\|ELPH_SELFEN_MU}}.

	Let us look at the following example. If ~~one sets~~		Let us look at the following example. If we set
	* {{TAGO\|ELPH_SCATTERING_APPROX\|SERTA MRTA_TAU}}		* {{TAGO\|ELPH_SCATTERING_APPROX\|SERTA MRTA_TAU}}
	* {{TAGO\|ELPH_SELFEN_MU\|-0.1 0.0 0.1}}		* {{TAGO\|ELPH_SELFEN_MU\|-0.1 0.0 0.1}}

← Older revision		Revision as of 13:14, 20 October 2025
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	* {{TAG\|ELPH_SCATTERING_APPROX}}		* {{TAG\|ELPH_SCATTERING_APPROX}}
	* {{TAG\|ELPH_SELFEN_MU}}		* {{TAG\|ELPH_SELFEN_MU}}
			* {{TAG\|ELPH_SELFEN_MU_RANGE}}
	* {{TAG\|ELPH_SELFEN_CARRIER_DEN}}		* {{TAG\|ELPH_SELFEN_CARRIER_DEN}}
			* {{TAG\|ELPH_SELFEN_CARRIER_DEN_RANGE}}
	* {{TAG\|ELPH_SELFEN_CARRIER_PER_CELL}}		* {{TAG\|ELPH_SELFEN_CARRIER_PER_CELL}}
	* {{TAG\|ELPH_MODE}}		* {{TAG\|ELPH_MODE}}

← Older revision		Revision as of 08:47, 20 October 2025
Line 232:		Line 232:
	* [[Bandgap_renormalization_due_to_electron-phonon_coupling\|Band-structure renormalization]]		* [[Bandgap_renormalization_due_to_electron-phonon_coupling\|Band-structure renormalization]]
	* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]		* [[Transport coefficients including electron-phonon scattering\|Transport calculations]]
			* [[Chemical potential]]
	* {{TAG\|ELPH_SCATTERING_APPROX}}		* {{TAG\|ELPH_SCATTERING_APPROX}}
	* {{TAG\|ELPH_SELFEN_MU}}		* {{TAG\|ELPH_SELFEN_MU}}