ABINIT Discussion Forums

Hello there,
How to determine the relationship between pressure and elastic constant, as well as Born effective charge?
According to the tutorial, when we calculate crystal parameters and some physical properties, some common variables were mentioned using the DFPT method. But I am not sure which one is used to determine the relationship between pressure and the results we calculated.
In the **.out files, there are some stress tensors, for instance,
Cartesian components of stress tensor (hartree/bohr^3)
sigma(1 1)= -7.62016028E-07 sigma(3 2)= 0.00000000E+00
sigma(2 2)= -7.62016028E-07 sigma(3 1)= 0.00000000E+00
sigma(3 3)= -1.18852361E-06 sigma(2 1)= 0.00000000E+00
I just think the stress tensors are from the displacement of ion or atom. But if it really has something to so with pressure, how can I obtain that mentioned elationship ?
Hope for your reply, thanks!

Best wishes
nannan

Hi!

Relationship between the pressure and elastic constants is something what you should calculate by yourself. Just use abinit and dfpt to calculate elastic constants at various pressures. That's it.

The pressure is outputted in your output file just after the components of the stress tensor. It's calculated as the minus average of the diagonal components.

Also, stress is obtained from the response with respect to the strain of the unit cell, not the atomic displacements. The later in turn give phonons.

Hope this helps.

Igor L.

Hi I will to know
How to determine the relationship between Rigid-atom elastic tensor and 2DErelax
best regard

ghahmed wrote:Hi I will to know
How to determine the relationship between Rigid-atom elastic tensor and 2DErelax
best regard

Hi!

Please, go through the elastic tutorial

http://www.abinit.org/documentation/helpfiles/for-v7.2/tutorial/lesson_elastic.html.

There you will also find the references in which you can find the answers.

Best regards,

Igor