Bethe-Salpeter solver: diagonalization - Revision history

Fulvio: /* Choosing the input parameters */

2023-05-19T16:15:36Z

Choosing the input parameters

← Older revision		Revision as of 16:15, 19 May 2023
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	Copy the previous input file for the BSE kernel in a new one:		Copy the previous input file for the BSE kernel in a new one:

	$ cp 02_3D_BSE_kernel.in 03_3D_BSE_diago_solver.in		$ cp 02_3D_BSE_kernel.in 03_3D_BSE_diago_solver.in

	Invoke yambo with the "-y d" option in the command line. Also add "-V qp" to set qp corrections:		Invoke yambo with the "-y d" option in the command line. Also add "-V qp" to set qp corrections:

Fulvio: /* Bethe-Salpeter solver runlevel */

2022-04-06T13:05:35Z

Bethe-Salpeter solver runlevel

← Older revision		Revision as of 13:05, 6 April 2022
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	Take some time to inspect the log and the report to check the consistency with the input variables. This run produces a new database in the 3D_BSE directory		Take some time to inspect the log and the report to check the consistency with the input variables. This run produces a new database in the 3D_BSE directory
	3D_BSE/ndb.~~BS_diago_Q01~~		3D_BSE/ndb.BS_diago_Q1
	So if you need the spectrum on a different energy range, direction, with a different broadening or more points the diagonalization is not repeated, just the spectrum is recalculated.		So if you need the spectrum on a different energy range, direction, with a different broadening or more points the diagonalization is not repeated, just the spectrum is recalculated.
	Note that this database, as well as any other netCDF-format database produced by Yambo, can be directly accessed and read using [[First steps in Yambopy\| python modules]].		Note that this database, as well as any other netCDF-format database produced by Yambo, can be directly accessed and read using [[First steps in Yambopy\| python modules]].

Attacc: /* Choosing the input parameters */

2022-04-05T07:46:36Z

Choosing the input parameters

← Older revision		Revision as of 07:46, 5 April 2022
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	==Choosing the input parameters==		==Choosing the input parameters==

			Copy the previous input file for the BSE kernel in a new one:

			$ cp 02_3D_BSE_kernel.in 03_3D_BSE_diago_solver.in

	Invoke yambo with the "-y d" option in the command line. Also add "-V qp" to set qp corrections:		Invoke yambo with the "-y d" option in the command line. Also add "-V qp" to set qp corrections:

Fulvio: Update output of less o-3D_BSE.eps_q1_diago_bse

2021-04-14T14:49:07Z

Update output of less o-3D_BSE.eps_q1_diago_bse

← Older revision		Revision as of 14:49, 14 April 2021
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	$ less o-3D_BSE.eps_q1_diago_bse		$ less o-3D_BSE.eps_q1_diago_bse
	...		...
	#		#
	# E/ev[1] EPS-Im[2] EPS-Re[3] EPSo-Im[4] EPSo-Re[5]		# E/ev[1] EPS-Im[2] EPS-Re[3] EPSo-Im[4] EPSo-Re[5]
	#		#
	2.~~00000~~ 0.~~16162 5~~.~~83681~~ 0.~~04959 4~~.~~14127~~		2.00000000 0.596699752E-1 3.11588550 0.300982650E-1 2.50442362
	2.~~03015~~ 0.~~16787 5~~.~~88612~~ 0.~~05090 4~~.~~15638~~		2.03015089 0.607326068E-1 3.13400412 0.304788072E-1 2.51354647
			2.06030154 0.618246123E-1 3.15244579 0.308668576E-1 2.52278614
	...		...

Myrta: /* Bethe-Salpeter solver runlevel */

2021-04-14T12:54:33Z

Bethe-Salpeter solver runlevel

← Older revision		Revision as of 12:54, 14 April 2021
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	$ gnuplot		$ gnuplot
	...		...
	plot 'o-3D_BSE.eps_q1_diago_bse' u 1:2 w l t 'BSE', 'o-3D_BSE.eps_q1_diago_bse' u 1:5 w l t 'IPA'		plot 'o-3D_BSE.eps_q1_diago_bse' u 1:2 w l t 'BSE', 'o-3D_BSE.eps_q1_diago_bse' u 1:4 w l t 'IPA'

	[[file:03_bse_diago.png \|none\|600px]]		[[file:03_bse_diago.png \|none\|600px]]

Myrta: /* Bethe-Salpeter solver runlevel */

2021-04-14T12:49:35Z

Bethe-Salpeter solver runlevel

← Older revision		Revision as of 12:49, 14 April 2021
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	$ gnuplot		$ gnuplot
	...		...
	plot 'o-3D_BSE.eps_q1_diago_bse' u 1:2 w l t 'BSE', 'o-3D_BSE.eps_q1_diago_bse' u 1:4 w l t 'IPA'		plot 'o-3D_BSE.eps_q1_diago_bse' u 1:2 w l t 'BSE', 'o-3D_BSE.eps_q1_diago_bse' u 1:5 w l t 'IPA'

	[[file:03_bse_diago.png \|none\|600px]]		[[file:03_bse_diago.png \|none\|600px]]
	The addition of the kernel has the effect to red-shift the spectrum onset and redistribute the oscillator strengths.		The addition of the kernel has the effect to red-shift the spectrum onset and redistribute the oscillator strengths.

	Note that these calculations are not converged with respect to the k-point grid. The low energy peaks in the IPA are an artefact of poor convergence with k-points producing artificial confinement. Carrying out the convergence for k-points would smooth out these peak in the IPA spectrum to give the shoulder corresponding to the van Hove singularity in the band structure. On the other hand, the low energy peak in the BSE is genuine and it is the signature of a bound exciton. This will appear more clearly in [[How to choose the input parameters \| one of the next tutorials]] where we will perform the convergence with the k points.		Note that these calculations are not converged with respect to the k-point grid. The low energy peaks in the IPA are an artefact of poor convergence with k-points producing artificial confinement. Carrying out the convergence for k-points would smooth out these peak in the IPA spectrum to give the shoulder corresponding to the van Hove singularity in the band structure. On the other hand, the low energy peak in the BSE is genuine and it is the signature of a bound exciton. This will appear more clearly in [[How to choose the input parameters \| one of the next tutorials]] where we will perform the convergence with the k points.

	==Summary==		==Summary==

Davide: /* Choosing the input parameters */

2021-04-14T11:58:25Z

Choosing the input parameters

← Older revision		Revision as of 11:58, 14 April 2021
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	==Choosing the input parameters==		==Choosing the input parameters==

	Invoke yambo with the "-y d" option in the command line:		Invoke yambo with the "-y d" option in the command line. Also add "-V qp" to set qp corrections:

	$ yambo -F 03_3D_BSE_diago_solver.in -y d -V qp -J 3D_BSE		$ yambo -F 03_3D_BSE_diago_solver.in -y d -V qp -J 3D_BSE

Myrta at 18:36, 28 March 2021

2021-03-28T18:36:14Z

← Older revision		Revision as of 18:36, 28 March 2021
Line 114:		Line 114:

	[[file:03_bse_diago.png \|none\|600px]]		[[file:03_bse_diago.png \|none\|600px]]
	The addition of the kernel has the effect to red-shift the spectrum onset and redistribute the oscillator strengths. Note that the ~~convergence for~~ k-~~points smooths out the~~ low energy peaks in the IPA ~~(which~~ are an artefact of poor convergence with k-points producing artificial confinement) to give the shoulder corresponding to the van Hove singularity in the band structure. On the other hand, the low energy peak in the BSE is genuine and it is the signature of a bound exciton.		The addition of the kernel has the effect to red-shift the spectrum onset and redistribute the oscillator strengths.

			Note that these calculations are not converged with respect to the k-point grid. The low energy peaks in the IPA are an artefact of poor convergence with k-points producing artificial confinement. Carrying out the convergence for k-points would smooth out these peak in the IPA spectrum to give the shoulder corresponding to the van Hove singularity in the band structure. On the other hand, the low energy peak in the BSE is genuine and it is the signature of a bound exciton. This will appear more clearly in [[How to choose the input parameters \| one of the next tutorials]] where we will perform the convergence with the k points.

	==Summary==		==Summary==

Myrta at 18:31, 28 March 2021

2021-03-28T18:31:01Z

← Older revision		Revision as of 18:31, 28 March 2021
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	In this module, you learn how to obtain an optical absorption spectrum within the Bethe-Salpeter equation (BSE) framework by diagonalizing a previously calculated Bethe-Salpeter (BS) kernel.		In this module, you learn how to obtain an optical absorption spectrum within the Bethe-Salpeter equation (BSE) framework by diagonalizing a previously calculated Bethe-Salpeter (BS) kernel.

			'''Warning''': for this demonstration, we did not use converged parameters (in particular they are not converged for the k-grid). Note that one needs to converge carefully all parameters to obtain scientific relevant results. This will be the topic of [[How to choose the input parameters \| one of the next tutorials]].


	==Prerequisites==		==Prerequisites==

Myrta at 17:13, 28 March 2021

2021-03-28T17:13:46Z

← Older revision		Revision as of 17:13, 28 March 2021
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	'''You will need''':		'''You will need''':
	* The <code>SAVE</code> databases for 3D hBN		* The <code>SAVE</code> databases for 3D hBN
	* The <code>3D_QP_BSE</code> directory (provided) which contains the database with the GW corrections (create one directory with this name and put the ndb.QP file produced yesterday there)
	* The <code>3D_BSE</code> directory containing the databases from the [[Static screening]] and [[Bethe-Salpeter kernel]] modules		* The <code>3D_BSE</code> directory containing the databases from the [[Static screening]] and [[Bethe-Salpeter kernel]] modules
	* The <code>yambo</code> executable		* The <code>yambo</code> executable