[QE-users] Guidance Required for Stiffness Matrix Calculation from Stress and Strain Data

[Elham Rezaee]

Thank you so much for your generous offer to share the. I would love to take a look at it.

Could you please send me the spreadsheet ? It would be a great help for my current project.

Best,

Elham Rezaee

 PhD student at UNB/Canada

________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Marcelo Falcão de Oliveira via users <users at lists.quantum-espresso.org>
Sent: Wednesday, November 22, 2023 2:43 PM
To: Mpayami <mpayami at aeoi.org.ir>; Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: Re: [QE-users] Guidance Required for Stiffness Matrix Calculation from Stress and Strain Data

❗External message: Use caution.

Dear Rezaee,

  If it helps I have an excel spreadsheet that automatically calculates the elastic constants for you. You just copy and paste data from QE to the spreadsheet and vice versa. It automatically calculates 6 possible distortions for your unit cell, thus you run the QE calculations and paste back the stress matrices, thus you'll have all elastic constants. It also checks the stiffness matrix for elastic stability (eigenvalues) as well as calculates averages of Voigt, Reuss and Voigt-Reuss-Hill. The references used for all that are also cited in the spreadsheet. Just let me know.

Regards,

Em qua., 22 de nov. de 2023 às 14:46, Mpayami via users <users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>> escreveu:
Dear Elham,

Hi.
Once I was interested to do such direct calculations, I followed the method outlined in the following link:

https://docs.materialsproject.org/methodology/materials-methodology/elasticity

as well as the notes provided by Prof. Andrea Dal Corso in the DOC folder of Thermo_pw.

Secondly, as Prof. Nicola Marzari suggested in reply to your post, please mention your affiliation in your posts.

Hope that helps.

Besr regards,
Mahmoud Payami

NSTRI, AEOI
Tehran, Iran
Email: mpayami at aeoi.org.ir<mailto:mpayami at aeoi.org.ir>
Phone: +98(0)2182066504
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----- Original Message -----
________________________________
From: Elham Rezaee (elham.rezaee at unb.ca<mailto:elham.rezaee at unb.ca>)
Date: 01/09/1402 15:54
To: users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>
Subject: [QE-users] Guidance Required for Stiffness Matrix Calculation from Stress and Strain Data


Hi Team,

I am reaching out for some clarification on the procedure for calculating the stiffness matrix. I understand that it involves applying various strains to our crystalline structure and then measuring the corresponding stress matrices, but I am unsure about the details of this process.

My plan is to apply strains in the range of -1% to +1%. The approach, as I understand it, is to begin by adjusting the 'a' parameter in the x-direction by +1%, and then proceed to modify the other cell parameters such as 'ay', and so on. However, I am unclear about how to systematically organize the relationship between each applied strain and the resulting 3x3 stress tensor. This organization is crucial for the accurate assembly of the stiffness matrix.

Additionally, the sequence in which the cell parameters should be deformed is a point of uncertainty for me. A clear and systematic approach is necessary to ensure the correct construction of the stiffness matrix, which is essential for calculating the elastic properties of our material.

I aim to perform these calculations independently to acquire the stiffness matrix, like those found in the Material Project database, to further evaluate the material's elastic properties.

Could you please provide guidance or point me to resources that could help clarify how to properly organize the strain and stress matrices and determine the sequence of cell parameter deformations?

Thanks,
Elham

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people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
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