Nonlinear tensors of LiTaO3 and LiNbO3  [SOLVED]

Phonons, DFPT, electron-phonon, electric-field response, mechanical response…

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MarkusKonrad
Posts: 3
Joined: Sat Aug 11, 2018 4:01 pm

Nonlinear tensors of LiTaO3 and LiNbO3

Post by MarkusKonrad » Sun Aug 12, 2018 5:54 pm

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

ebousquet
Posts: 469
Joined: Tue Apr 19, 2011 11:13 am
Location: University of Liege, Belgium

Re: Nonlinear tensors of LiTaO3 and LiNbO3

Post by ebousquet » Thu Sep 06, 2018 2:24 pm

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

MarkusKonrad
Posts: 3
Joined: Sat Aug 11, 2018 4:01 pm

Re: Nonlinear tensors of LiTaO3 and LiNbO3

Post by MarkusKonrad » Fri Sep 07, 2018 11:08 am

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

mverstra
Posts: 655
Joined: Wed Aug 19, 2009 12:01 pm

Re: Nonlinear tensors of LiTaO3 and LiNbO3  [SOLVED]

Post by mverstra » Fri Sep 07, 2018 11:25 am

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.
Matthieu Verstraete
University of Liege, Belgium

MarkusKonrad
Posts: 3
Joined: Sat Aug 11, 2018 4:01 pm

Re: Nonlinear tensors of LiTaO3 and LiNbO3

Post by MarkusKonrad » Fri Sep 07, 2018 11:29 am

Dear Mathiew,

thank you for your answer!

best regards

Markus

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