Real time approach to linear response - Revision history

Petru Milev: Typo fixes

2024-10-21T07:54:52Z

Typo fixes

← Older revision		Revision as of 07:54, 21 October 2024
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	Use the command		Use the command
	yambo_nl -u -F Inputs_nl/01_td_ip.in		yambo_nl -u n -F Inputs_nl/01_td_ip.in

	to generate the input:		to generate the input:
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	Now we can use		Now we can use
	ypp_rt -t X -F Inputs_rt/ypp_abs.in		ypp_rt -n X -F Inputs_rt/ypp_abs.in

	to generate the input file		to generate the input file

Fulvio: /* Introduction */

2023-05-21T15:15:32Z

Introduction

← Older revision		Revision as of 15:15, 21 May 2023
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	In this example, we will consider a single layer of hexagonal boron nitride (hBN).		In this example, we will consider a single layer of hexagonal boron nitride (hBN).
	If you didn't before you can download input files and Yambo databases for this tutorial here: [~~http~~://~~www~~.yambo-code.~~org~~/educational/tutorials/files/hBN-2D-RT.tar.gz hBN-2D-RT.tar.gz].		If you didn't before you can download input files and Yambo databases for this tutorial here: [https://media.yambo-code.eu/educational/tutorials/files/hBN-2D-RT.tar.gz hBN-2D-RT.tar.gz].
	and/or follow the instructions to generate the databases here: [[Prerequisites for Real Time propagation with Yambo]]		and/or follow the instructions to generate the databases here: [[Prerequisites for Real Time propagation with Yambo]]

Davide: /* Approach based on the Berry Phase */

2023-05-19T14:53:02Z

Approach based on the Berry Phase

← Older revision		Revision as of 14:53, 19 May 2023
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	There are few differences which could be due to the following reasons:		There are few differences which could be due to the following reasons:
	* Coupling with the external field: the <code>yambo_rt</code> evaluates the coupling with the external field through the dipoles (by default computing the commutator [x,Hnl]; the <code>yambo_nl</code> evaluates the coupling using an expression based on the Berry Phase. For the latter, a numerical differentiation in reciprocal space is performed. The 10x10 2D k-mesh may not be fine enough. For denser k-mesh, the Berry phase approach converges to the one based on the dipoles. To avoid this one can use <code>DipApproach="Covariant"</code> in the scheme used by yambo_rt.		* Coupling with the external field: the <code>yambo_rt</code> evaluates the coupling with the external field through the dipoles (by default computing the commutator [x,Hnl]; the <code>yambo_nl</code> evaluates the coupling using an expression based on the Berry Phase. For the latter, a numerical differentiation in reciprocal space is performed. The 10x10 2D k-mesh may not be fine enough. For denser k-mesh, the Berry phase approach converges to the one based on the dipoles. To avoid this one can use <code>DipApproach="Covariant"</code> in the scheme used by yambo_rt.
	* Integrator: the integrator used for the <code>yambo_nl</code> is more accurate. The fact that the differences are more pronounced for long times may hint to inaccuracies in the integration of the equation of motions in <code>yambo_rt</code>. One can use a similar integrator with yambo_rt, by setting in input <code>Integrator= "~~EULER~~ RK2"</code>		* Integrator: the integrator used for the <code>yambo_nl</code> is more accurate. The fact that the differences are more pronounced for long times may hint to inaccuracies in the integration of the equation of motions in <code>yambo_rt</code>. One can use a similar integrator with yambo_rt, by setting in input <code>Integrator= "INV RK2"</code>

	==Results Analysis==		==Results Analysis==

Davide: /* Approach based on the Berry Phase */

2023-05-19T14:52:42Z

Approach based on the Berry Phase

← Older revision		Revision as of 14:52, 19 May 2023
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	In the plot the polarization from the two different propagation schemes are compared.		In the plot the polarization from the two different propagation schemes are compared.
	There are few differences which could be due to the following reasons:		There are few differences which could be due to the following reasons:
	* with <code>yambo_rt</code> the dipoles ~~evaluated via~~ [x,Hnl] ~~are used. On~~ the ~~other hand with~~ <code>yambo_nl</code> the ~~dipoles computed via~~ the ~~Covariant approach are used~~. ~~The~~ latter ~~converge to the former if the k-points sampling of the Brillouine zone~~ is ~~dense enough~~. a 10x10 2D mesh ~~could~~ not be enough		* Coupling with the external field: the <code>yambo_rt</code> evaluates the coupling with the external field through the dipoles (by default computing the commutator [x,Hnl]; the <code>yambo_nl</code> evaluates the coupling using an expression based on the Berry Phase. For the latter, a numerical differentiation in reciprocal space is performed. The 10x10 2D k-mesh may not be fine enough. For denser k-mesh, the Berry phase approach converges to the one based on the dipoles. To avoid this one can use <code>DipApproach="Covariant"</code> in the scheme used by yambo_rt.
	* the integrator used ~~with~~ <code>yambo_nl</code> is more ~~precise~~. ~~Indeed~~ the differences are more pronounced for long times		* Integrator: the integrator used for the <code>yambo_nl</code> is more accurate. The fact that the differences are more pronounced for long times may hint to inaccuracies in the integration of the equation of motions in <code>yambo_rt</code>. One can use a similar integrator with yambo_rt, by setting in input <code>Integrator= "EULER RK2"</code>

	==Results Analysis==		==Results Analysis==

Davide: /* Approach based on the density matrix */

2020-01-30T15:58:12Z

Approach based on the density matrix

← Older revision		Revision as of 15:58, 30 January 2020
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	negf # [R] Real-Time dynamics		negf # [R] Real-Time dynamics
	RT_Threads=0 # [OPENMP/RT] Number of threads for real-time		RT_Threads=0 # [OPENMP/RT] Number of threads for real-time
	HXC_Potential= "IP" # [SC] SC HXC Potential		HXC_Potential= <span style="color:red">"IP"</span> # [SC] SC HXC Potential
	% RTBands		% RTBands
	<span style="color:red">3</span> \| <span style="color:red">6</span> \| # [RT] Bands		<span style="color:red">3</span> \| <span style="color:red">6</span> \| # [RT] Bands
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	Field1_Width= 0.000000 fs # [RT Field1] Width		Field1_Width= 0.000000 fs # [RT Field1] Width
	Field1_kind= "<span style="color:red">DELTA</span>" # [RT Field1] Kind(SIN\|RES\|ANTIRES\|GAUSS\|DELTA\|QSSIN)		Field1_kind= "<span style="color:red">DELTA</span>" # [RT Field1] Kind(SIN\|RES\|ANTIRES\|GAUSS\|DELTA\|QSSIN)
	Field1_pol= "linear" # [RT Field1] Pol(linear\|circular)		Field1_pol= "<span style="color:red">linear</span>" # [RT Field1] Pol(linear\|circular)
	% Field1_Dir		% Field1_Dir
	0.000000 \| <span style="color:red">1.000000</span> \| 0.000000 \| # [RT Field1] Versor		0.000000 \| <span style="color:red">1.000000</span> \| 0.000000 \| # [RT Field1] Versor

Claudio: /* Approach based on the Berry Phase */

2020-01-30T15:06:02Z

Approach based on the Berry Phase

← Older revision		Revision as of 15:06, 30 January 2020
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	to generate the input:		to generate the input:

	~~nlinear~~ # [R NL] Non-linear optics		nloptics # [R NL] Non-linear optics
	NL_Threads= 1 # [OPENMP/NL] Number of threads for nl-optics		NL_Threads= 1 # [OPENMP/NL] Number of threads for nl-optics
	% NLBands		% NLBands

Claudio: /* Introduction */

2020-01-30T14:07:30Z

Introduction

← Older revision		Revision as of 14:07, 30 January 2020
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	If you didn't before create an Inputs folder and then the input file with the commands		If you didn't before create an Inputs folder and then the input file with the commands
	mkdir Inputs		mkdir Inputs
	~~yambo~~ -o c -F Inputs/01_ip.in		yambo_nl -o c -F Inputs/01_ip.in
	and set the proper input parameters		and set the proper input parameters
	optics # [R OPT] Optics		optics # [R OPT] Optics
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	%		%
	and then run the code		and then run the code
	~~yambo~~ -F Inputs/01_ip.in -J CHI_IP -C CHI_IP		yambo_nl -F Inputs/01_ip.in -J CHI_IP -C CHI_IP

	The resulting spectrum will give an idea of the energy involved in the real-time simulations		The resulting spectrum will give an idea of the energy involved in the real-time simulations

Davide: /* Approach based on the density matrix */

2020-01-30T13:26:44Z

Approach based on the density matrix

← Older revision		Revision as of 13:26, 30 January 2020
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	Use the command		Use the command
	yambo_rt -p p -F Inputs_rt/01_td_ip.in		yambo_rt -n p -F Inputs_rt/01_td_ip.in

	to generate the input:		to generate the input:

Davide: /* Approach based on the Berry Phase */

2020-01-29T21:14:23Z

Approach based on the Berry Phase

← Older revision		Revision as of 21:14, 29 January 2020
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	{\| style="width:100%" border="1"		{\| style="width:100%" border="1"
	\|style="width:15%; text-align:left"\|Prev: [[Prerequisites_for_Real_Time_propagation_with_Yambo\|Prerequisites]]		\|style="width:15%; text-align:left"\|Prev: [[Prerequisites_for_Real_Time_propagation_with_Yambo\|Prerequisites]]
	\|style="width:70%; text-align:center"\|Now: [[~~ICTP2020~~\|~~ICTP~~ Tutorials]] --> [[Linear response from real time simulations\|Linear Response]] --> [[Real time approach to linear response\|Independent Particles ]]		\|style="width:70%; text-align:center"\|Now: [[Tutorials\|Tutorials]] --> [[Linear response from real time simulations\|Linear Response]] --> [[Real time approach to linear response\|Independent Particles ]]
	\|style="width:35%; text-align:right"\|Next: [[Real time Bethe-Salpeter Equation (TDSE)]]		\|style="width:35%; text-align:right"\|Next: [[Real time Bethe-Salpeter Equation (TDSE)]]
	\|-		\|-
	\|}		\|}

Davide: Renamed ypp input file

2020-01-24T09:50:22Z

Renamed ypp input file

← Older revision		Revision as of 09:50, 24 January 2020
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	Now we can use		Now we can use
	ypp_rt -t X -F Inputs_rt/~~01_td_ip_ypp~~.in		ypp_rt -t X -F Inputs_rt/ypp_abs.in

	to generate the input file		to generate the input file
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	where we set a Lorentzian smearing corresponding to 0.1 eV. Notice that due to the finite time of our simulation smearing is always necessary to Fourier transform the result.		where we set a Lorentzian smearing corresponding to 0.1 eV. Notice that due to the finite time of our simulation smearing is always necessary to Fourier transform the result.
	Then we run		Then we run
	ypp_rt -F Inputs_rt/~~01_td_ip_ypp~~.in -J TD-IP_rt -C TD-IP_rt		ypp_rt -F Inputs_rt/ypp_abs.in -J TD-IP_rt -C TD-IP_rt
	and obtain the files for the dielectric constant along with the field direction, the EELS along with the same direction, and the damped polarization.		and obtain the files for the dielectric constant along with the field direction, the EELS along with the same direction, and the damped polarization.
	o-TD-IP_rt.YPP-eps_along_E		o-TD-IP_rt.YPP-eps_along_E
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	Now we can use		Now we can use
	ypp_nl -u -F Inputs_nl/~~01_td_ip_ypp~~.in		ypp_nl -u -F Inputs_nl/ypp_abs.in

	to generate the input file:		to generate the input file:
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	where we set a Lorentzian smearing corresponding to 0.1 eV. Notice that due to the finite time of our simulation smearing is always necessary to Fourier transform the result.		where we set a Lorentzian smearing corresponding to 0.1 eV. Notice that due to the finite time of our simulation smearing is always necessary to Fourier transform the result.
	Then we run		Then we run
	ypp_nl -F Inputs_nl/~~01_td_ip_ypp~~.in -J TD-IP_nl -C TD-IP_nl		ypp_nl -F Inputs_nl/ypp_abs.in -J TD-IP_nl -C TD-IP_nl
	and obtain the files for the dielectric constant along with the field direction, the EELS along with the same direction, and the damped polarization.		and obtain the files for the dielectric constant along with the field direction, the EELS along with the same direction, and the damped polarization.
	o-TD-IP_nl.YPP-eps_along_E		o-TD-IP_nl.YPP-eps_along_E