VASP Computing Elastic Constants of Si - Revision history

Yanmingw: /* Analyze data */

2015-09-06T05:40:06Z

Analyze data

← Older revision		Revision as of 05:40, 6 September 2015
Line 311:		Line 311:
	The second lines computes the C11 and C12 elastic constants and the third line calculates C44. Suggested results are C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa for calculations with US-LDA PP.		The second lines computes the C11 and C12 elastic constants and the third line calculates C44. Suggested results are C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa for calculations with US-LDA PP.

	<span style="background:yellow">'''C44 data we got here is much smaller than the paper's result of 105 GPa but is the same as the experimental value of 76 GPa. We suspect maybe 105 GPa is the unrelaxed result since only specifying ISIF=2 doesn't enable relaxation. ''' <\span>		<span style="background:yellow">'''C44 data we got here is much smaller than the paper's result of 105 GPa but is the same as the experimental value of 76 GPa. We suspect maybe 105 GPa is the unrelaxed result since only specifying ISIF=2 doesn't enable relaxation. ''' </span>

Yanmingw: /* Analyze data */

2015-09-06T05:37:43Z

Analyze data

← Older revision		Revision as of 05:37, 6 September 2015
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	The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively. The parameter '''2''' specifies the number of atoms in the computation cell and '''8''' is the number of atoms in a conventional unit cell.		The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively. The parameter '''2''' specifies the number of atoms in the computation cell and '''8''' is the number of atoms in a conventional unit cell.
	The second lines computes the C11 and C12 elastic constants and the third line calculates C44. Suggested results are C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa for calculations with US-LDA PP.		The second lines computes the C11 and C12 elastic constants and the third line calculates C44. Suggested results are C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa for calculations with US-LDA PP.

			<span style="background:yellow">'''C44 data we got here is much smaller than the paper's result of 105 GPa but is the same as the experimental value of 76 GPa. We suspect maybe 105 GPa is the unrelaxed result since only specifying ISIF=2 doesn't enable relaxation. ''' <\span>

Yanmingw at 09:31, 4 September 2015

2015-09-04T09:31:48Z

← Older revision		Revision as of 09:31, 4 September 2015
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	<pre>		<pre>
	#!/bin/bash		#!/bin/bash
	#PBS -N vasp.Si.~~C11~~		#PBS -N vasp.Si.C44
	#PBS -j oe		#PBS -j oe
	#PBS -l nodes=1:ppn=8,walltime=48:00:00		#PBS -l nodes=1:ppn=8,walltime=48:00:00
Line 309:		Line 309:

	The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively. The parameter '''2''' specifies the number of atoms in the computation cell and '''8''' is the number of atoms in a conventional unit cell.		The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively. The parameter '''2''' specifies the number of atoms in the computation cell and '''8''' is the number of atoms in a conventional unit cell.
	The second lines computes the C11 and C12 elastic constants and the third line calculates C44. ~~You~~ ~~should~~ ~~obtain~~ C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa for calculations with US-LDA PP.		The second lines computes the C11 and C12 elastic constants and the third line calculates C44. Suggested results are C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa for calculations with US-LDA PP.

Yanmingw: /* Analyze data */

2015-09-04T08:02:56Z

Analyze data

← Older revision		Revision as of 08:02, 4 September 2015
Line 303:		Line 303:
	Place the data files of <tt>Elatt.C11.dat</tt>, <tt>Elatt.C44.dat</tt>, <tt>Elatt.B.dat</tt> from [[VASP_Computing_Bulk_Modulus_of_Si \| Bulk modulus calculation of Si]]		Place the data files of <tt>Elatt.C11.dat</tt>, <tt>Elatt.C44.dat</tt>, <tt>Elatt.B.dat</tt> from [[VASP_Computing_Bulk_Modulus_of_Si \| Bulk modulus calculation of Si]]

	Launch <tt>Matlab</tt>,		Launch <tt>Matlab</tt>, and type the following commands.
	[a0, Ecoh, B] = fit_a0EB('Elatt.B.dat',2,8);		[a0, Ecoh, B] = fit_a0EB('Elatt.B.dat',2,8);
	[C11,C12] = fit_C11EB('Elatt.C11.dat',a0,B);		[C11,C12] = fit_C11EB('Elatt.C11.dat',a0,B);

Yanmingw: /* Analyze data */

2015-09-04T08:02:28Z

Analyze data

← Older revision		Revision as of 08:02, 4 September 2015
Line 309:		Line 309:

	The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively. The parameter '''2''' specifies the number of atoms in the computation cell and '''8''' is the number of atoms in a conventional unit cell.		The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively. The parameter '''2''' specifies the number of atoms in the computation cell and '''8''' is the number of atoms in a conventional unit cell.
	The second lines computes the C11 and C12 elastic constants and the third line calculates C44. You should obtain C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa.		The second lines computes the C11 and C12 elastic constants and the third line calculates C44. You should obtain C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa for calculations with US-LDA PP.

Yanmingw: /* Analyze data */

2015-09-04T08:02:00Z

Analyze data

← Older revision		Revision as of 08:02, 4 September 2015
Line 272:		Line 272:
	After running the two scripts above for C11 and C44, the data files: <tt>Elatt.C11.dat</tt> and <tt>Elatt.C44.dat</tt> will be created.		After running the two scripts above for C11 and C44, the data files: <tt>Elatt.C11.dat</tt> and <tt>Elatt.C44.dat</tt> will be created.

			If you choose your POTCAR for US-LDA PP, the date should be similar to
⚫	~~One example of~~ <tt>Elatt.C11.dat</tt> is

		⚫	<tt>Elatt.C11.dat</tt>
	<pre>		<pre>
	0.997 1 -.47813207E+02 -.47813293E+02 -.478132E+02		0.997 1 -.47813207E+02 -.47813293E+02 -.478132E+02
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	</pre>		</pre>

	~~ONe example of~~ <tt>Elatt.C44.dat</tt> is		<tt>Elatt.C44.dat</tt>
	<pre>		<pre>
	0.997 3 -.95626284E+02 -.95626386E+02 -.264643E-03		0.997 3 -.95626284E+02 -.95626386E+02 -.264643E-03
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	C44 = fit_C44EB('Elatt.C44.dat',a0,C11,C12);		C44 = fit_C44EB('Elatt.C44.dat',a0,C11,C12);

		⚫	The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively. The parameter '''2''' specifies the number of atoms in the computation cell and '''8''' is the number of atoms in a conventional unit cell.
	In MATLAB click "change folder" when you open the file and remove the semicolon to run it from the command line.
		⚫	The second lines computes the C11 and C12 elastic constants and the third line calculates C44. You should obtain C11 = 161 GPa, C12 = 63 GPa and C44 = 76 GPa.
⚫	The first line fits the energy data to a quadratic curve and computes the equilibrium lattice constant, cohesive energy and bulk modulus(['''a0, Ecoh, B]''') respectively.
	Refer to previous calculation?!)
⚫	The second lines computes the C11 and C12 elastic constants and the third line calculates C44. You should obtain C11 = 161 GPa, C12 = ~~179.2~~ GPa and C44 = 42 GPa.

Yanmingw at 03:31, 3 September 2015

2015-09-03T03:31:01Z

← Older revision		Revision as of 03:31, 3 September 2015
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	1.003 3 -.95626329E+02 -.95626438E+02 -.252950E-03		1.003 3 -.95626329E+02 -.95626438E+02 -.252950E-03
	</pre>		</pre>

	Launch <tt>octave</tt> and run the following functions
			Download the following Matlab functions.
	[[media:fit_a0EB.m.txt \| fit_a0EB.m]],		[[media:fit_a0EB.m.txt \| fit_a0EB.m]],
	[[media:fit_C11EB.m.txt \| fit_C11EB.m]],		[[media:fit_C11EB.m.txt \| fit_C11EB.m]],
	[[media:fit_C44EB.m.txt \| fit_C44EB.m]],		[[media:fit_C44EB.m.txt \| fit_C44EB.m]],

			Place the data files of <tt>Elatt.C11.dat</tt>, <tt>Elatt.C44.dat</tt>, <tt>Elatt.B.dat</tt> from [[VASP_Computing_Bulk_Modulus_of_Si \| Bulk modulus calculation of Si]]
	Run '''cal_VASP.m''' in Matlab,

			Launch <tt>Matlab</tt>,
	fit_a0EB('Elatt.B.dat',4,4);
	~~fit_C11EB~~('Elatt.~~C11~~.dat',a0,B);		[a0, Ecoh, B] = fit_a0EB('Elatt.B.dat',2,8);
	~~fit_C44EB~~('Elatt.~~C44~~.dat',a0,~~C11,C12~~);		[C11,C12] = fit_C11EB('Elatt.C11.dat',a0,B);
			C44 = fit_C44EB('Elatt.C44.dat',a0,C11,C12);

	In MATLAB click "change folder" when you open the file and remove the semicolon to run it from the command line.		In MATLAB click "change folder" when you open the file and remove the semicolon to run it from the command line.
Line 308:		Line 310:
	Refer to previous calculation?!)		Refer to previous calculation?!)
	The second lines computes the C11 and C12 elastic constants and the third line calculates C44. You should obtain C11 = 161 GPa, C12 = 179.2 GPa and C44 = 42 GPa.		The second lines computes the C11 and C12 elastic constants and the third line calculates C44. You should obtain C11 = 161 GPa, C12 = 179.2 GPa and C44 = 42 GPa.

	===Parallel computation===

	To run <tt>vasp</tt> in parallel, you need to submit [[media:vasp.pbs.txt \| vasp.pbs]] as

	qsub vasp.pbs


	You will need the following two files to do this calculation in parallel on SU-AHPCRC:
	[[media:auto.B.par.Au.txt \| auto.B.par]] and
	[[media:B.pbs.Au.txt \| B.pbs]].

Yanmingw at 03:23, 3 September 2015

2015-09-03T03:23:28Z

@@ Line 270: / Line 270: @@
 ===Analyze data===
-After running the two scripts above for C11 and C44, it will create the data files: <tt>Elatt.C11.dat</tt> and  <tt>Elatt.C44.dat</tt>.
+After running the two scripts above for C11 and C44, the data files: <tt>Elatt.C11.dat</tt> and  <tt>Elatt.C44.dat</tt> will be created.
 Launch <tt>octave</tt> and run the following functions
 [[media:fit_a0EB.m.txt | fit_a0EB.m]],

Yanmingw: /* Analyze data */

2015-09-03T03:17:11Z

Analyze data

← Older revision		Revision as of 03:17, 3 September 2015
Line 270:		Line 270:
	===Analyze data===		===Analyze data===

	After running the two scripts above for C11 and C44, ~~<tt>./auto.B.serial</tt>~~ it will create the data files: <tt>Elatt.C11.dat</tt>~~,<tt>platt.C11.dat</tt>,~~ ~~<tt>Elatt.C44.dat</tt>,~~ ~~and~~ <tt>~~platt~~.C44.dat</tt>.		After running the two scripts above for C11 and C44, it will create the data files: <tt>Elatt.C11.dat</tt> and <tt>Elatt.C44.dat</tt>.

			<tt>Elatt.C11.dat</tt>

Yanmingw: /* Run VASP */

2015-09-02T06:51:53Z

Run VASP

← Older revision		Revision as of 06:51, 2 September 2015
Line 98:		Line 98:
	===Run VASP===		===Run VASP===

	To compute the elastic constants, we prepared the following PBS scripts to submit the jobs to MC2 cluster. <tt>vasp.pbs.C11</tt> is used to to run <tt>vasp</tt> repeated with different values for the first component of the first Bravais lattice vector, '''$a'''. Here we put 5.402856 as the length of the lattice constant in the script. In generally, you are expected to put a reliable value from your lattice constant calculation with the same PP. The script automatically creates the POSCAR file for every '''a''' specified in the script in the range from 0.997 to 1.003. For C44 calculation, the PBS script <tt>vasp.pbs.C44</tt> changes the value of '''"$a"''' for the first and second component of the first Bravais lattice vector.		To compute the elastic constants, we prepared the following PBS scripts to submit the jobs to MC2 cluster. <tt>vasp.pbs.C11</tt> is used to to run <tt>vasp</tt> repeated with different values for the first component of the first Bravais lattice vector, '''$a'''. Here we put 5.402856 as the length of the lattice constant in the script. In generally, you are expected to put a reliable value from your lattice constant calculation with the same PP. The script automatically creates the POSCAR file for every '''a''' specified in the script in the range from 0.997 to 1.003. For C44 calculation, the PBS script <tt>vasp.pbs.C44</tt> changes the value of '''$a''' for the first and second component of the first Bravais lattice vector.

	'''PBS script for C11'''		'''PBS script for C11'''