Hi,
First thank you for reading my post.
I have calculated the isothermal elastic constant by using QHA. Now I want to get the adiabatic elastic constants.I know the conversion factor but confused about the term "derivative of entropy with respect to strain".
I am using the strain-energy relations to calculate the 3 elastic constant for cubic MgO. I used 3 different deformation matrices to get those elastic constant. I used phonopy for the QHA calculation. So from phonopy output I can get the temperature vs entropy for a particular deformation but not the strain. So it will be of great help if anyone suggest me on how to get the ∂S/∂eii (eii= component of strain tensor).
Regards,
Pratik
Dear Pratik Kumar Das
From the theoretical point of view, that should be done with the Ehrenfest relations. Please you can check the book on statistical physics by Landau and Lifshitz, the chapter on second-order phase transitions.
Please check also the following reference to look at how the Ehrenfest relations look in the case of the strain tensor.
Article Theory of elastic properties of Sr2RuO4 at the superconducti...
Dear Prof. Pedro L. Contreras E.
Thank you for pointing this out. It helps me to understand it properly.
As I was using QHA, I already calculated thermal expansion. I used this expansion for the conversion from isothermal to adiabatic elastic constants (Theory of elasticity, Landau and Lifshitz).
Thank you very much once again for your kind help.
Best regards
Pratik
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