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

[Marcelo Falcão de Oliveira]

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> 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
> Phone: +98(0)2182066504
> ------------------------------------
>
> ----- Original Message -----
> ------------------------------
> From: Elham Rezaee (elham.rezaee at unb.ca)
> Date: 01/09/1402 15:54
> To: 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
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
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-- 
Marcelo Falcão de Oliveira
Professor Associado
Departamento de Engenharia de Materiais
EESC - USP
Av. João Dagnone, 1100,  Jd. Sta Angelina
CEP: 13563-120, São Carlos - SP - Brasil
e-mail: marcelo.falcao at usp.br
Fone: (16) 3373-9583
Fax: (16) 3373-9590
Agenda:
http://www.google.com/calendar/embed?src=marcelo.falcao%40usp.br&ctz=America/Sao_Paulo&mode=week
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