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

[Elham Rezaee]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20231122/bebc7d46/attachment.html>