Equilibrium volume of Si in the RPA - Revision history

Karsai: /* Download */

2019-11-14T13:21:27Z

Download

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	{{Template:GW - Tutorial}}		{{Template:GW - Tutorial}}

	~~Back to the [[The_VASP_Manual\|main page]].~~

	[[Category:Examples]]		[[Category:Examples]]

2019-11-14T08:48:43Z

Download

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	== Download ==		== Download ==
	[~~http~~:~~//www.vasp.at/vasp-workshop/examples/Si_ACFDT_vol~~.tgz Si_ACFDT_vol.tgz]		[[Media:Si ACFDT vol.tgz\| Si_ACFDT_vol.tgz]]

	{{Template:GW - Tutorial}}		{{Template:GW - Tutorial}}

2019-06-24T17:20:47Z

Running this example

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	== Running this example ==		== Running this example ==

	The following bash-script <code>doall.sh</code> will run through all of the aforementioned calculational steps (step 1-5) for a range of different lattice constants (''a=5.1-5.8''Å in steps of ''0.1''Å)		The following bash-script <code>doall.sh</code> will run through all of the aforementioned calculational steps (step 1-5) for a range of different lattice constants (''a=5.1-5.8'' Å in steps of ''0.1'' Å)

	<pre>		<pre>

2019-06-24T17:20:22Z

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	*The RPA total energy is calculated as the, ''E(RPA)=EC(RPA)+EXX'', the sum of the RPA correlation energy of step 5 ''EC(RPA)'' and the Hartree fock energy ''EXX'' of step 2.		*The RPA total energy is calculated as the, ''E(RPA)=EC(RPA)+EXX'', the sum of the RPA correlation energy of step 5 ''EC(RPA)'' and the Hartree fock energy ''EXX'' of step 2.
	:To get the Hartree fock energy <code>grep “free energy”</code> in the OUTCAR.EXX.* file (there are two spaces between free and energy).		:To get the Hartree fock energy <code>grep “free energy”</code> in the OUTCAR.EXX.* file (there are two spaces between free and energy).


	== Running this example ==		== Running this example ==

2019-06-24T17:19:40Z

Task

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	The workflow of a RPA total energy calculations consists of five consecutive steps:		The workflow of a RPA total energy calculations consists of five consecutive steps:

	*Step 1: a “standard” DFT groundstate calculation with a “dense” mesh of k-points.		# a “standard” DFT groundstate calculation with a “dense” mesh of k-points.
	*Step 2: compute the Hartree-Fock energy using the DFT orbitals of Step 1. Needs {{TAG\|WAVECAR}} file from step 1.		# compute the Hartree-Fock energy using the DFT orbitals of Step 1. Needs {{TAG\|WAVECAR}} file from step 1.
	*Step 3: a “standard” DFT groundstate calculation with “coarse” mesh of k-points.		# a “standard” DFT groundstate calculation with “coarse” mesh of k-points.
	*Step 4: obtain DFT “virtual” orbitals (empty states). Needs {{TAG\|WAVECAR}} file from step 3.		# obtain DFT “virtual” orbitals (empty states). Needs {{TAG\|WAVECAR}} file from step 3.
	*Step 5: the RPA correlation energy (ACFDT) calculation. Needs {{TAG\|WAVECAR}} and {{TAG\|WAVEDER}} files from step 4.		# the RPA correlation energy (ACFDT) calculation. Needs {{TAG\|WAVECAR}} and {{TAG\|WAVEDER}} files from step 4.

	In case of metallic systems there is an additional step between Steps 4 and 5, that is beyond the		In case of metallic systems there is an additional step between Steps 4 and 5, that is beyond the

2019-06-24T17:17:28Z

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	*Using {{TAG\|NBANDS}}=4 only occupied states are considered to save time.		*Using {{TAG\|NBANDS}}=4 only occupied states are considered to save time.


	=== Step 3: DFT groundstate calculation with a “coarse” mesh of k-points ===		=== Step 3: DFT groundstate calculation with a “coarse” mesh of k-points ===

	*Perform a DFT groundstate calculation with a “coarse” mesh of k-points.		*Perform a DFT groundstate calculation with a “coarse” mesh of k-points.
			:This is the mesh of k-points that will be used in the subsequent ACFDT calculation.

	*The following {{TAG\|INCAR}} file is used (INCAR.DFT):		*The following {{TAG\|INCAR}} file is used (INCAR.DFT):

2019-06-24T17:13:16Z

Step 2: Compute the Hartree-Fock energy using the DFT orbitals

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	*The {{TAG\|INCAR}} file INCAR.EXX is used in this step:		*The {{TAG\|INCAR}} file INCAR.EXX is used in this step:
	~~<pre>~~
	{{TAGBL\|ALGO}} = EIGENVAL ; {{TAGBL\|NELM}} = 1		{{TAGBL\|ALGO}} = EIGENVAL ; {{TAGBL\|NELM}} = 1
	{{TAGBL\|LWAVE}} = .FALSE.		{{TAGBL\|LWAVE}} = .FALSE.
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	{{TAGBL\|KPAR}} = 8		{{TAGBL\|KPAR}} = 8
	{{TAGBL\|NBANDS}} = 4		{{TAGBL\|NBANDS}} = 4
	~~</pre>~~

	*{{TAG\|NKRED}}=2 is used for the downsample the k-space representation of the Fock-potential to save time.		*{{TAG\|NKRED}}=2 is used for the downsample the k-space representation of the Fock-potential to save time.

	*Using {{TAG\|NBANDS}}=4 only occupied states are considered to save time.		*Using {{TAG\|NBANDS}}=4 only occupied states are considered to save time.


	=== Step 3: DFT groundstate calculation with a “coarse” mesh of k-points ===		=== Step 3: DFT groundstate calculation with a “coarse” mesh of k-points ===

2019-06-24T17:10:34Z

Running this example

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	*To quickly visualize ~~the output for~~ the total energy vs. lattice-constant curves for DFT and RPA ~~you may run~~:		* When everything is finished you can quickly visualize (with gnuplot) the total energy vs. lattice-constant curves for DFT and RPA by means of:

	./plotall.sh		./plotall.sh

2019-06-24T17:09:15Z

Running this example

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	done		done
	</pre>		</pre>

			To execute the aforementions script:

			./doall.sh

2019-06-24T17:08:04Z

Task

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	scope of this example.		scope of this example.

	To compute the equilibrium lattice constant of Si we need to calculate the RPA total energy for a range of different lattice constants.		'''N.B.:'''To compute the equilibrium lattice constant of Si we need to calculate the RPA total energy for a range of different lattice constants.
	All of the calculation steps are prepared automatically performed by the script ''doall.sh'' (see below):		All of the calculation steps are prepared automatically performed by the script ''doall.sh'' (see below):

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	*The {{TAG\|INCAR}} file INCAR.EXX is used in this step:		*The {{TAG\|INCAR}} file INCAR.EXX is used in this step:
	~~<pre>~~
	{{TAGBL\|ALGO}} = EIGENVAL ; {{TAGBL\|NELM}} = 1		{{TAGBL\|ALGO}} = EIGENVAL ; {{TAGBL\|NELM}} = 1
	{{TAGBL\|LWAVE}} = .FALSE.		{{TAGBL\|LWAVE}} = .FALSE.
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	{{TAGBL\|KPAR}} = 8		{{TAGBL\|KPAR}} = 8
	{{TAGBL\|NBANDS}} = 4		{{TAGBL\|NBANDS}} = 4
	~~</pre>~~

	*{{TAG\|NKRED}}=2 is used for the downsample the k-space representation of the Fock-potential to save time.		*{{TAG\|NKRED}}=2 is used for the downsample the k-space representation of the Fock-potential to save time.

	*Using {{TAG\|NBANDS}}=4 only occupied states are considered to save time.		*Using {{TAG\|NBANDS}}=4 only occupied states are considered to save time.


	=== Step 3: DFT groundstate calculation with a “coarse” mesh of k-points ===		=== Step 3: DFT groundstate calculation with a “coarse” mesh of k-points ===