ABINIT Discussion Forums

Dear community,

can abinit compute nonlinear tensors of Lithium niobate and lithium tantalate?
I would need nonlinear Piezo- Stiffness, electrostriction etc..

Thank you for your advice in advance!

best regards

Markus

Dear Markus,
At present the only non-linear properties (3rd orders) that can be computed directly with DFPT are the electro-optic coefficients and raman tensors (meaning with intensities).
For the other cases, you should combine 2nd order DFPT and frozen phonon (direct method) techniques (for electrostriction, etc).
All the best,
Eric

Dear Eric,

thank you for your answer! Does this imply that also for elastic third order tensors 3rd order DFPT is not available?

best regards
Markus

This is thinkable, but extremely complex. You would probably want to do it with mathematica and dump the code directly. For some terms this is what Don Hamann did in the original implementation of the strain DFPT.

Dear Mathiew,

thank you for your answer!

best regards

Markus