My Community

May I ask you a question about ferroelectric dipole moment calculation?
I did not attach INCAR or other files because I follow exactly same
example in below links.
In vasp there are two ways of calculating FE dipole moment:

http://cms.mpi.univie.ac.at/vasp/vasp/L ... again.html
http://cms.mpi.univie.ac.at/vasp/vasp/L ... _tags.html

on the links there are example of
NaF
4.5102
0.0 0.5 0.5
0.5 0.0 0.5
0.5 0.5 0.0
1 1
Direct
0.0000000000000000 0.0000000000000000 0.0000000000000000
0.5000000000000000 0.5000000000000000 0.5000000000000000


and I can get the same results:
electronic dipole moment: p[elc]=( 0.00000 0.00000 0.00000
) electrons Angst

If we move all atoms by same vectors, the dipole moment should not
change, right? So I tried the following,
NaF
4.5102
0.0 0.5 0.5
0.5 0.0 0.5
0.5 0.5 0.0
1 1
Direct
0.0000000000000000 0.0000000000000000 0.0100000000000000
0.5000000000000000 0.5000000000000000 0.5100000000000000



But the results now change! Becomes:
macroscopic dipole moment: p[mac]=( 0.36081 0.36081
0.00000 ) electrons Angst

I tried moving all atoms by other vectors and they all change. So if
we calculate PVDF's moment,
we put one PVDF wire in a supercell, I will get different results
depending on where I put it in
supercell: center or margin leads to completely dipole moment.

,do I misunderstand
something? Thank you very
much and your help is highly appreciated!

Hi,

We're sorry that we didn’t answer your question. This does not live up to the quality of support that we aim to provide. The team has since expanded. If we can still help with your problem, please ask again in a new post, linking to this one, and we will answer as quickly as possible.

Best wishes,

VASP