tdep-developers/tdep

[ERROR] Born effective charge not Hermitian

Closed this issue · 1 comments

kli103 commented

Hi,

I was trying to include LOTO to phonon in extract_forceconstant. The symmetry of the material I am studying is low, and the Born effective charge tensor is not symmetryic. TDEP showed the following error:
... Born charges not Hermitian, error: 8.2344767095669359E-007
... DISPERSIONS MIGHT BE IRREGULAR!
... FIXME!

This error causes incorrect phonon dispersion.

But some previous discussion indicates that the Born effective charge needs not be Hermitian. http://www.democritos.it/pipermail/pw_forum/2006-January/003511.html

Could you resolve this issue? The log files can be found in the zip file attached.
extract_forceconstants_rc5_skip_400_loto.zip

flokno commented

Hi @kli103 ,

right now, the only reliable workaround is to use tdep_simplify_bec from https://github.com/flokno/tools.tdep via

tdep_simplify_bec infile.lotosplitting

and use the resulting outfile.lotosplitting. This will symmetrize the BEC and make them effectively scalar. Unfortunately there is currently no better solution.