...DIPOL Flag in Berry`s phase calculations...

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brocks
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...DIPOL Flag in Berry`s phase calculations...

#1 Post by brocks » Tue Feb 13, 2007 5:14 pm

Dear Users,

imperforminm not able to understand the words of the manual to describe the DIPOL flag:
"This tag specifies the origin with respect to which the ionic contribution to the dipole moment in the cell is calculated. When comparing changes in this contribution due to the displacement of an ion, this center should be chosen in such a way that the ions in the distorted and the undistorted structure remain on the same side of DIPOL (in terms of a minimum image convention)"
Practically what does it mean?

Then i would ask an other thing.
The values of DIPOL flag i have to give to the sets of my calculations (because i have a POSCAR for centro and non-centrosymmetric structures), i believe, must correspond to the same point in cartesian coordinates.
Is this true?

Replies are welcome.
Thank you.
Gianluca.
Last edited by brocks on Tue Feb 13, 2007 5:14 pm, edited 1 time in total.

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...DIPOL Flag in Berry`s phase calculations...

#2 Post by admin » Thu Mar 08, 2007 8:21 am

1) you are right, you have to do the complete set of calculations for both of the phases.
2) this comment about the DIPOL means that it has to be set in such a way that the direction of the dipole moments must not revert before and after the displacement of the atoms which you have to introduce to get a certain polarization mode. If your cell geometries do not differ too much, the centers of the dipoles may be the same.
However, in principle, DIPOL has to be set for each structure separeately.
Last edited by admin on Thu Mar 08, 2007 8:21 am, edited 1 time in total.

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