Solution LAB1 diamond bulk modulus - Revision history

Andrea Ferretti: /* Bulk modulus of diamond */

2020-12-16T13:10:10Z

Bulk modulus of diamond

← Older revision		Revision as of 13:10, 16 December 2020
Line 11:		Line 11:
	* The above steps are coded in the script <code>./LabQSM/tools/compute_B_modulus.py</code> for convenience		* The above steps are coded in the script <code>./LabQSM/tools/compute_B_modulus.py</code> for convenience

	Results as a function of the kinetic energy cutoff ~~follow.~~
			'''Results as a function of the kinetic energy cutoff''' are reported below:

	# ecut [Ry] B modulus [GPa]		# ecut [Ry] B modulus [GPa]

Andrea Ferretti: /* Bulk modulus of diamond */

2020-12-16T13:09:37Z

Bulk modulus of diamond

← Older revision		Revision as of 13:09, 16 December 2020
Line 12:		Line 12:

	Results as a function of the kinetic energy cutoff follow.		Results as a function of the kinetic energy cutoff follow.

			# ecut [Ry] B modulus [GPa]
			20 4222.035362534261
			30 545.8276696265291
			40 577.6525328096515
			50 678.313290451693
			60 526.4841165649044
			80 463.3508978235948
			100 471.6781060558174
			120 468.6260793219729
			140 467.798081344509
			160 467.04233495671605

			Once again, a cutoff of 60-80 Ry (80 better) seems to be sufficient.

			A script to automate the calculation can be put together as follows:

			#!/bin/bash

			list=`ls results_*_vol.dat`
			fileout=results_BMOD.dat

			echo "# ecut [Ry] B modulus [GPa]" > $fileout

			for file in $list
			do
			filein=$file
			ecut=`echo $file \| cut -d "_" -f2 \| sed 's/Ry//'`
			bmod=`./compute_B_modulus.py $file \| tail -1 \| awk '{print $(NF-1)}'`
			echo $ecut $bmod >> $fileout
			done

Andrea Ferretti: Created page with " * Back to the previous page: Structural and electronic properties of semiconductors and metals #Convergences ===Bulk modulus of diamond=== Using the data produced in th..."

2020-12-16T12:20:28Z

Created page with " * Back to the previous page: Structural and electronic properties of semiconductors and metals #Convergences ===Bulk modulus of diamond=== Using the data produced in th..."

New page

* Back to the previous page: [[Structural and electronic properties of semiconductors and metals #Convergences]]

===Bulk modulus of diamond===

Using the data produced in the previous exercise (total energy as a function of the lattice parameter for a range of ecutwfc values), one can do the following:
* extract etot vs volume for each wfcutfc value into different files;
* fit the data and extract the second derivative in the minimum;
* this can be done using a second (or better higher) order polynomial or other fitting functions (cubic splines, [https://en.wikipedia.org/wiki/Birch–Murnaghan_equation_of_state Murnaghan equation of state], ...)
* Evaluate the bulk modulus taking care of unit conversion to international system (B modulus is given in GPa)
* The above steps are coded in the script <code>./LabQSM/tools/compute_B_modulus.py</code> for convenience

Results as a function of the kinetic energy cutoff follow.