I am wondering what piezoelectric constant in the 3x6 Voigt form should we use, the “PIEZOELECTRIC TENSOR for field in x, y, z”, the “PIEZOELECTRIC TENSOR IONIC CONTR for field in x, y, z”, or the summation of the two? Please let me know.
Many thanks in advance.

Thanks for the reply @alex . But I am not able to properly follow your reply. IN OUTCAR, it writes both “PIEZOELECTRIC TENSOR for field in x, y, z” and “PIEZOELECTRIC TENSOR IONIC CONTR for field in x, y, z”. By full piezoelectric tensor, do you mean the summation of the two ?

Dear @alex,
Please let me know which one of the two piezoelectric tensor written in OUTCAR file should we take.
Is it: (i) “PIEZOELECTRIC TENSOR for field in x, y, z”
(ii) “PIEZOELECTRIC TENSOR IONIC CONTR for field in x, y, z”.
Thank you.