Proper piezoelectric tensor

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phenyl

Proper piezoelectric tensor

#1 Post by phenyl » Thu May 26, 2011 1:57 am

Dear Vasp-Users,

I would like to know whether the "relaxed-ion piezoelectric tensor" PIEZOELECTRIC TENSOR for field in x, y, z in the OUTCAR) as specified in [1] is the _proper_ piezoelectric tensor ( e$_{\alpha \beta \gamma}$ /e$_{\alpha j}$?

Thank you very much for your help

[1] http://cms.mpi.univie.ac.at/vasp/vasp/V ... ensor.html
Last edited by phenyl on Thu May 26, 2011 1:57 am, edited 1 time in total.

jacekwu
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Re: Proper piezoelectric tensor

#2 Post by jacekwu » Mon Jun 29, 2020 11:43 am

Hi phenyl

9 years later, I am here asking the same question...

Have you found the answer?

Best wishes
Jacek

martin.schlipf
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Re: Proper piezoelectric tensor

#3 Post by martin.schlipf » Tue Jun 30, 2020 6:29 am

This page of the manual explains what exactly is calculated by Vasp.

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Re: Proper piezoelectric tensor

#4 Post by jacekwu » Tue Jun 30, 2020 7:42 am

Hi Martin

Thanks for your reply. Can I clarify with you the following?

According to the manual entry on IBRION=6 , inversion of ionic Hessian matrix and its multiplication with the internal strain tensor are calculated as described in ref 4 (i.e. PhysRevB.72.035105) and the pieozelectric tensor can be calculated using the LEPSILON = TRUE .

However, PhysRevB.72.035105 notes that "there is some subtlety in the definition of the piezoelectric tensors related to the specification of the
energy functional when both fields and strains are present, leading to a distinction between “proper” and “improper” piezoelectric constants."

In LEPSILON tag's manual entry you attached, it is not mentioned how the piezoelectric tensor is calculated; however in theory, as the internal strain tensor is involved in the relaxed-ion piezoelectric tensor, I suppose VASP is using the approach presented in PhysRevB.72.035105. Can I verify with you if this is correct?
Also, as it is not mentioned explicitly that VASP is calculating the "proper" tensors as presented by PhysRevB.72.035105, can I also verify with you that VASP is indeed calculating the "proper" terms instead of the "improper" terms?

Thanks
Yaze

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Re: Proper piezoelectric tensor

#5 Post by martin.schlipf » Wed Jul 01, 2020 5:19 am

In this reference, the implementation in Vasp is documented in more detail. Unfortunately, you need to confirm for yourself, whether that is equivalent to the reference that you mention.

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Re: Proper piezoelectric tensor

#6 Post by jacekwu » Wed Jul 01, 2020 9:27 am

Thanks Martin!

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