Category:Dielectric properties - Revision history

Csheldon: /* Additional resources */

2026-03-24T13:56:48Z

Additional resources

← Older revision		Revision as of 13:56, 24 March 2026
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	== Additional resources ==		== Additional resources ==
	=== Lectures ===		=== Lectures ===
	*Lecture on ~~[https~~:~~//youtu.be/3YKJZHmcGhY~~ dielectric properties from first principles].		*Lecture on {{Video\|dielectric:pedro:2025\|dielectric properties from first principles}}.
	*Lecture on the ~~[https~~:~~//youtu.be/6F_WNIh6V7I~~ optical bandgap].		*Lecture on the {{Video\|optical:merzuk:2025\|optical bandgap}}.

	=== Tutorials ===		=== Tutorials ===
	*Tutorials for ~~[https~~:~~//vasp.at/tutorials/latest/response/~~ linear response].		*Tutorials for {{Tutorial\|response:part1\|linear response}}.
	*Tutorials for ~~[https~~:~~//vasp.at/tutorials/latest/gw/~~ GW].		*Tutorials for {{Tutorial\|gw:part1\|GW approximation}}.
	*Tutorials for ~~[https://vasp.at/tutorials/latest/~~bse/ BSE].		*Tutorials for {{Tutorial\|bse\|Bethe-Salpeter equation (BSE)}}.

	== References ==		== References ==

	[[Category:VASP\|Dielectric Functions]] [[Category:Linear response]]		[[Category:VASP\|Dielectric Functions]] [[Category:Linear response]]

Csheldon: /* Tutorials */

2026-02-12T10:55:04Z

Tutorials

← Older revision		Revision as of 10:55, 12 February 2026
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	where <math>e_{\alpha j}</math> is the ion-relaxed piezoelectric tensor.		where <math>e_{\alpha j}</math> is the ion-relaxed piezoelectric tensor.

	== Tutorials ==		== Additional resources ==
			=== Lectures ===
			*Lecture on [https://youtu.be/3YKJZHmcGhY dielectric properties from first principles].
			*Lecture on the [https://youtu.be/6F_WNIh6V7I optical bandgap].
			=== Tutorials ===
	*Tutorials for [https://vasp.at/tutorials/latest/response/ linear response].		*Tutorials for [https://vasp.at/tutorials/latest/response/ linear response].
	*Tutorials for [https://vasp.at/tutorials/latest/gw/ GW].		*Tutorials for [https://vasp.at/tutorials/latest/gw/ GW].
	*Tutorials for [https://vasp.at/tutorials/latest/bse/ BSE].		*Tutorials for [https://vasp.at/tutorials/latest/bse/ BSE].
	*Lecture on [https://youtu.be/3YKJZHmcGhY dielectric properties from first principles].
	*Lecture on the [https://youtu.be/6F_WNIh6V7I optical bandgap].

	== References ==		== References ==

	[[Category:VASP\|Dielectric Functions]] [[Category:Linear response]]		[[Category:VASP\|Dielectric Functions]] [[Category:Linear response]]

Csheldon: /* Dielectric function */

2026-01-22T13:59:38Z

Dielectric function

← Older revision		Revision as of 13:59, 22 January 2026
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	::<math>D_\alpha(\omega) = \epsilon_{\alpha\beta}(\omega)E_\beta(\omega) </math>.		::<math>D_\alpha(\omega) = \epsilon_{\alpha\beta}(\omega)E_\beta(\omega) </math>.

	Depending on the nature of the external field, there are different approaches for the calculation of <math>\epsilon</math>. If <math>\mathbf E</math> is static, then one can rely on perturbative methods based on finite differences or density functional perturbation theory (DFPT). However, if the perturbation is a time-dependent <math>\mathbf E</math>-field, (e.g., in measurements of the optical absorption, reflectance, magneto-optical Kerr effect (MOKE), etc.), the response will depend on the frequency of the external field. For these cases, one must employ methods based on time-dependent linear response, (e.g., Green-Kubo) or many-body perturbation theory.		Depending on the nature of the external field, there are different approaches for the calculation of <math>\epsilon</math>. If <math>\mathbf E</math> is static, then one can rely on perturbative methods based on finite differences or [[Electric field response from density-functional-perturbation theory \| density functional perturbation theory]] (DFPT). However, if the perturbation is a time-dependent <math>\mathbf E</math>-field, (e.g., in measurements of the optical absorption, reflectance, magneto-optical Kerr effect (MOKE), etc.), the response will depend on the frequency of the external field. For these cases, one must employ methods based on time-dependent linear response, (e.g., Green-Kubo) or many-body perturbation theory.

	Below we present an overview of all possible cases where VASP employs either one of such methods for the calculation of <math>\epsilon</math>.		Below we present an overview of all possible cases where VASP employs either one of such methods for the calculation of <math>\epsilon</math>.
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	==== {{TAG\|LEPSILON}}: density-functional-perturbation theory (DFPT) ====		==== {{TAG\|LEPSILON}}: density-functional-perturbation theory (DFPT) ====

	:By setting {{TAG\|LEPSILON}}=.True., VASP uses DFPT to compute the static ion-clamped dielectric matrix with or without local field effects ({{TAG\|LRPA}}). Derivatives are evaluated using Sternheimer equations, avoiding the explicit computation of derivatives of the periodic part of the wave function. This method does not require the inclusion of empty states via {{TAG\|NBANDS}}.		:By setting {{TAG\|LEPSILON}}=.True., VASP uses [[Electric field response from density-functional-perturbation theory \| DFPT]] to compute the static ion-clamped dielectric matrix with or without local field effects ({{TAG\|LRPA}}). Derivatives are evaluated using Sternheimer equations, avoiding the explicit computation of derivatives of the periodic part of the wave function. This method does not require the inclusion of empty states via {{TAG\|NBANDS}}.

	:At the end of the calculation, both the values of <math>\epsilon</math> including ({{TAG\|LRPA}}=.True.) or excluding ({{TAG\|LRPA}}=.False.) local-field effects are printed in the {{TAG\|OUTCAR}} file. Perform a consistency check by comparing the values excluding local-field effects and static limit of <math>\epsilon</math> obtained with {{TAG\|LOPTICS}}=.True., i.e., <math>\lim_{\omega\to0}\epsilon(\omega)</math>.		:At the end of the calculation, both the values of <math>\epsilon</math> including ({{TAG\|LRPA}}=.True.) or excluding ({{TAG\|LRPA}}=.False.) local-field effects are printed in the {{TAG\|OUTCAR}} file. Perform a consistency check by comparing the values excluding local-field effects and static limit of <math>\epsilon</math> obtained with {{TAG\|LOPTICS}}=.True., i.e., <math>\lim_{\omega\to0}\epsilon(\omega)</math>.
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	:Regarding the comparison with optical experiments, (e.g., absorption, MOKE, reflectance), <math>q</math> is the photon momentum. Often, the <math>\mathbf q \to 0</math> limit is considered. Furthermore, the coupling between the resonant and anti-resonant terms can be switched off, in what is called the [[Bethe-Salpeter equations#Theory#Tamm-Dancoff approximation\|Tamm-Dancoff approximation]]. This approximation can be activated with the variable {{TAG\|ANTIRES}} set to 0. Setting this variable to 1 or 2 will include the coupling, but increase the computational cost.		:Regarding the comparison with optical experiments, (e.g., absorption, MOKE, reflectance), <math>q</math> is the photon momentum. Often, the <math>\mathbf q \to 0</math> limit is considered. Furthermore, the coupling between the resonant and anti-resonant terms can be switched off, in what is called the [[Bethe-Salpeter equations#Theory#Tamm-Dancoff approximation\|Tamm-Dancoff approximation]]. This approximation can be activated with the variable {{TAG\|ANTIRES}} set to 0. Setting this variable to 1 or 2 will include the coupling, but increase the computational cost.

	==Level of approximation==		==Level of approximation==
	===Microscopic and macroscopic quantities===		===Microscopic and macroscopic quantities===

Csheldon: /* Low-frequency corrections from atomic displacements */

2026-01-22T13:55:16Z

Low-frequency corrections from atomic displacements

← Older revision		Revision as of 13:55, 22 January 2026
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	Here <math>Z^*_{J\beta\delta'}</math> are the Born effective charges and <math>\varepsilon_{J\delta',\nu}(\mathbf{q = 0})</math> are the eigendisplacements associated with the vibration mode <math>\nu</math> for atom <math>J</math> along direction <math>\delta'</math>. More information on the theory and methods behind the computation of phonon frequencies and eigendisplacements can be found in the [[Phonons:_Theory\|phonons]] dedicated page.		Here <math>Z^*_{J\beta\delta'}</math> are the Born effective charges and <math>\varepsilon_{J\delta',\nu}(\mathbf{q = 0})</math> are the eigendisplacements associated with the vibration mode <math>\nu</math> for atom <math>J</math> along direction <math>\delta'</math>. More information on the theory and methods behind the computation of phonon frequencies and eigendisplacements can be found in the [[Phonons:_Theory\|phonons]] dedicated page.

	Inclusion of the low-frequency corrections can be activated in the {{TAG\|INCAR}} file with either {{TAG\|IBRION}} = 5,6 (~~DFPT~~) or 7,8 (~~finite differences~~), and by setting to .True. the variables {{TAG\|LEPSILON}} or {{TAG\|LCALCEPS}}.		Inclusion of the low-frequency corrections can be activated in the {{TAG\|INCAR}} file with either {{TAG\|IBRION}} = 5,6 (finite differences) or 7,8 (DFPT), and by setting to .True. the variables {{TAG\|LEPSILON}} or {{TAG\|LCALCEPS}}.

	====Polar materials====		====Polar materials====

Tal: /* X-ray absorption */

2025-10-17T09:21:35Z

X-ray absorption

@@ Line 189: / Line 189: @@
 ===X-ray absorption===
-[[:XAS|Core-state excitations]] can be modeled using two main approaches: the [[Supercell core-hole calculations|supercell core-hole method]] and the [[Bethe-Salpeter equation for core excitations|Bethe–Salpeter equation]]. In both cases, the interaction between the excited electron and the core hole is included explicitly.
+[[:XAS|Core-state excitations]] can be modeled using two main approaches:
 ===Reflectance===

Tal: /* X-ray absorption */

2025-10-17T09:03:04Z

X-ray absorption

← Older revision		Revision as of 09:03, 17 October 2025
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	===X-ray absorption===		===X-ray absorption===
	[[:XAS\|Core-state excitations]] can be modeled using two main approaches: [[Supercell core-hole calculations\|supercell core-hole method]] and [[Bethe-Salpeter equation for core excitations\|Bethe–Salpeter equation]]. ~~Both approaches account for~~ the interaction between the excited electron and the core hole.		[[:XAS\|Core-state excitations]] can be modeled using two main approaches: the [[Supercell core-hole calculations\|supercell core-hole method]] and the [[Bethe-Salpeter equation for core excitations\|Bethe–Salpeter equation]]. In both cases, the interaction between the excited electron and the core hole is included explicitly.

	===Reflectance===		===Reflectance===

Tal: /* X-ray absorption */

2025-10-17T08:58:45Z

X-ray absorption

← Older revision		Revision as of 08:58, 17 October 2025
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	===X-ray absorption===		===X-ray absorption===
	[[:XAS\|Core-state excitations]] can be modeled using two main approaches: ~~the~~ [[Supercell core-hole calculations\|supercell core-hole method]] and ~~the~~ [[Bethe-Salpeter equation for core excitations\|Bethe–Salpeter equation]]. Both approaches account for the interaction between the excited electron and the core hole.		[[:XAS\|Core-state excitations]] can be modeled using two main approaches: [[Supercell core-hole calculations\|supercell core-hole method]] and [[Bethe-Salpeter equation for core excitations\|Bethe–Salpeter equation]]. Both approaches account for the interaction between the excited electron and the core hole.

	===Reflectance===		===Reflectance===

Tal: /* X-ray absorption */

2025-10-17T08:58:19Z

X-ray absorption

← Older revision		Revision as of 08:58, 17 October 2025
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	===X-ray absorption===		===X-ray absorption===
	[[:XAS\|Core-state excitations]] can be modeled using two main approaches: the [[Supercell core-hole calculations\|supercell core-hole method]] and the [[Bethe-Salpeter equation for core excitations\|Bethe–Salpeter equation ~~(BSE)~~]]. Both approaches account for the interaction between the excited electron and the core hole.		[[:XAS\|Core-state excitations]] can be modeled using two main approaches: the [[Supercell core-hole calculations\|supercell core-hole method]] and the [[Bethe-Salpeter equation for core excitations\|Bethe–Salpeter equation]]. Both approaches account for the interaction between the excited electron and the core hole.

	===Reflectance===		===Reflectance===

Tal: /* Other dielectric properties */

2025-10-17T08:57:40Z

Other dielectric properties

← Older revision		Revision as of 08:57, 17 October 2025
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	\alpha(\omega) = \frac{2\omega}{c}k(\omega).		\alpha(\omega) = \frac{2\omega}{c}k(\omega).
	</math>		</math>

			===X-ray absorption===
			[[:XAS\|Core-state excitations]] can be modeled using two main approaches: the [[Supercell core-hole calculations\|supercell core-hole method]] and the [[Bethe-Salpeter equation for core excitations\|Bethe–Salpeter equation (BSE)]]. Both approaches account for the interaction between the excited electron and the core hole.

	===Reflectance===		===Reflectance===

Csheldon at 10:32, 22 September 2025

2025-09-22T10:32:21Z

← Older revision		Revision as of 10:32, 22 September 2025
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	:Regarding the comparison with optical experiments, (e.g., absorption, MOKE, reflectance), <math>q</math> is the photon momentum. Often, the <math>\mathbf q \to 0</math> limit is considered. Furthermore, the coupling between the resonant and anti-resonant terms can be switched off, in what is called the [[Bethe-Salpeter equations#Theory#Tamm-Dancoff approximation\|Tamm-Dancoff approximation]]. This approximation can be activated with the variable {{TAG\|ANTIRES}} set to 0. Setting this variable to 1 or 2 will include the coupling, but increase the computational cost.		:Regarding the comparison with optical experiments, (e.g., absorption, MOKE, reflectance), <math>q</math> is the photon momentum. Often, the <math>\mathbf q \to 0</math> limit is considered. Furthermore, the coupling between the resonant and anti-resonant terms can be switched off, in what is called the [[Bethe-Salpeter equations#Theory#Tamm-Dancoff approximation\|Tamm-Dancoff approximation]]. This approximation can be activated with the variable {{TAG\|ANTIRES}} set to 0. Setting this variable to 1 or 2 will include the coupling, but increase the computational cost.

	~~== Tutorials ==~~
	*Tutorials in []
	*Lecture on [https://youtu.be/3YKJZHmcGhY dielectric function.]

	==Level of approximation==		==Level of approximation==
	===Microscopic and macroscopic quantities===		===Microscopic and macroscopic quantities===
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	*Tutorials for [https://vasp.at/tutorials/latest/bse/ BSE].		*Tutorials for [https://vasp.at/tutorials/latest/bse/ BSE].
	*Lecture on [https://youtu.be/3YKJZHmcGhY dielectric properties from first principles].		*Lecture on [https://youtu.be/3YKJZHmcGhY dielectric properties from first principles].
	~~<!--~~*Lecture on the [https://youtu.be/6F_WNIh6V7I optical bandgap].~~-->~~		*Lecture on the [https://youtu.be/6F_WNIh6V7I optical bandgap].

	== References ==		== References ==

	[[Category:VASP\|Dielectric Functions]] [[Category:Linear response]]		[[Category:VASP\|Dielectric Functions]] [[Category:Linear response]]