Dear Sir,

I would recommend the following article (attached below)

It explains how to obtain some of the elastic constants.

In principle, you can start varying the lattice parameter in order to obtain the bulk modulus. If you are using QE, the examples from the version 4.3.2 are very useful. e.g.: espresso-4.3.2-examples.tar.gz

This file can be found on the qe-forge.org:  http://qe-forge.org/gf/project/q-e/frs/?action=FrsReleaseBrowse&frs_package_id=18&_br_pkgrls_total=50&_br_pkgrls_page=2

Article FIRST-PRINCIPLES STUDY ON MECHANICAL PROPERTIES OF CH4 HYDRATE

Hello!

There are two ways to compute the elastic constants Cij:

1) Via energy x strain relations.

2) Via stress x strain relations:

sij = Cijkl ekl (1)

where sij is the stress, Cijkl the elastic coefficients and ekl the strain. Einstein summation convention is used.

To calculate Cij with QE, I recommend the second one. 

Basically, the procedure is to apply strains in the unit cell and run a scf calculation to compute the stress. Which strains you will apply depend on the symmetry of your system and on the Cij you are interested. For instance, if you want to compute C11, you apply a strain in the x direction. Playing with relation (1) you can properly choose the strain.

You apply positive and negative strains and, since the stress x strain relation is linear, you fit a straight line.

If you need more help with elasticity theory, I recommend this book:

http://www.amazon.com/Crystal-Acoustics-Introduction-Study-Elastic/dp/0816262020

I am also attaching a paper where I calculated NaCl elastic constants, maybe it can help you.

Article Accurate thermoelastic tensor and acoustic velocities of NaCl

Hi Michael,

Your answer is quite helpful. I applied strains (+- 0.5%, +- 1% and +-1.5 %) in each of the x, y and z directions using Quantum Expresso. Now in order to calculate the elastic constants (assuming shear components to be zero), how can first calculate stress corresponding to each of those strains?

Hi Agrawal,

I am a new user. where I can apply strains in the Quantum Expresso.

Please I need your help.

Hi everybody? please I need your help how I can get in detailed step the elastic constants using QE

Please Use the Elastic software interface to QE.

Please follow the steps:

1. Install elastic package and give the path as mentioned in the software.

2.Add all the executables to bashrc

3.Prepare one of your optimized input file (i.e, scf.in)

4. ElaStic_Setup_Espresso

please enter the values when it is requested.

5. I will create Dst01 and Dst 02 (i.e, stress and strain method)

6. Then run QE calculations for each distortion.

8.Just come main directory and run executable :> Elastic_Analyze

9. It will create Elastic.2nd.in 

10. enter eta_max and polynomial fit order and Run

11..Elastic_Result

12. Elastic_2nd_out file will be generated and it consists of all of your results.

All the best.

@Kotagiri Sir,

I tried to calculate but the error is displayed as;

Energy ---=> 1

Stress ---=> 2

>>>> Please choose the method of the calculation (choose 1 or 2): 1

2nd ---=> 2

3rd ---=> 3

>>>> Please choose the order of the elastic constant (choose 2 or 3): 2

.... Oops NOTICE: ElaStic found "ElaStic_PW.in". It will be used as input file.

.... Oops sh: 1: sgroup: not found

So what can i do for correcting it ??

I encountered same problem, help

I did upto

$ Elastic_Setup_ESPRESS

It ha generated many distotred structures.

But I have no idea how to run each of them. Running scf one by one i a lengthy task. Somebody help me some easy method may be a script.

@Kotagiri Gangaprasad

http://exciting.wikidot.com/forum/t-1256461

#!/bin/sh

PW_COMMAND="pw.x" #echo "$PWD" #echo "$PW_COMMAND" for dir in Dst*/Dst* do for file_a in $dir/* do temp_file=$file_a echo $temp_file done $PW_COMMAND < $temp_file>""${temp_file%%.*}".out" done

Use pw_thermo the one that already comes with espresso latest version. Just run the scf and rest of the part thermo_pw will do for you.

Greetings to all,

Please suggest me, how can we calculate the elastic constant of 2D system using thermo_pw?

i will be very thankful to you!

i got an error

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%      Error in routine initialize_elastic_cons (1):      Laue class not available  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%      stopping ... -------------------------------------------------------------------------- MPI_ABORT was invoked on rank 2 in communicator MPI_COMM_WORLD with errorcode 1. NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes. You may or may not see output from other processes, depending on exactly when Open MPI kills them.

Hi Anisha Lamba , try to set the verborsity to high in your scf input file and run again.

I was also searching for the same when I was trying to calculate Cijs and I thermo_pw very easy to calculate.

This get easily interfaced with quantum espresso and just by running ow.x you get the values of Cij.

for details check the link below:

https://dalcorso.github.io/thermo_pw/

you have to use a package Elastic or thermo_pw

Thanks all,

Mr. Israel Olowookere , I have taken verborsity high already but have not got any result. May you please share your email id.

Anisha Lamba [email protected]

Dear all,

I am here to know that how to calculate Elastic constant using VASP ? I did calculation and what will be the next step ?

Shivam Kansara Tewodros Eyob Ada I faced the same error that states the following:

~/ElaStic_1.0$ $ElaSticROOT/ElaStic_Setup_ESPRESSO

Energy ---=> 1

Stress ---=> 2

>>>> Please choose the method of the calculation (choose 1 or 2): 1

2nd ---=> 2

3rd ---=> 3

>>>> Please choose the order of the elastic constant (choose 2 or 3): 2

.... Oops NOTICE: ElaStic found "ElaStic_PW.in". It will be used as input file.

.... Oops sh: 1: sgroup: not found

May I please know how did you resolve it?

I have tried to do calculation for elastic constants using thermo_pw code but unable to do.

I have got the following error:

thermo_pw.x command no found

Please suggest

Dear Shahram Yalameha

Thank you.

I have done the calculation for elastic constants.

You may use thermo pw package which is compatible with Quantum espresso.

https://dalcorso.github.io/thermo_pw/

Do not use thermo_pw module, it's a junk not supported by its developer having a very brief documentation that won't help you figure out troubles and having a particularly horrific usability. Elastic set of scripts should help you and anyone else trying to calculate elastic constants using QE.

http://exciting.wikidot.com/carbon-elastic

Elastic creates a set of individual input files for QE which can be submitted as a job array in Slurm or executed in series, whichever is more practical.