Is it possible to calculate surface polarity using Berry phase calculations

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fatihgsen · #1 Post by **fatihgsen** » Tue Sep 09, 2008 9:17 pm

Dear All,

I would like to calculate the surface polarity. Is it possible to compute using VASP's Berry phase module. If it is not possible could you please give me some advice.

Thanks in advance.

#2 Post by **admin** » Wed Sep 17, 2008 3:02 pm

please define 'surface polarity' more closely:
1) if you want to calculate the dipole moment of a slab, please set IDIPOL according to the direction of the surface normal
2) the polarization of a surface can be calculated using the Berry phase approach as implemented in VASP. Please keep in mind that
--) the periodicity is broken across the surface normal (IGPAR need not be taken along this direction)
--) please also don't forget to check that the surface has to be insulating!

fatihgsen · #3 Post by **fatihgsen** » Wed Sep 24, 2008 8:54 pm

Thank you for very much for your help. I want to characterize the polar property of the surface. I thought the polarization is informative for me. I tried to do a Berry phase calculation on a diamond surface but VASP could not do it. The surface normal is on z-direction and when I set IGPAR=1 VASP fails with an error

VERY BAD NEWS! internal error in subroutine PRICEL (probably precision problem, try to change SYMPREC in INCAR ?):
Sorry, number of cells and number of vectors did not agree. 4

There was not any problem when I set IGPAR=2 or 3. I tried to change SYMPREC but nothing changed. This happened for both distorted or undistorted lattice. What could be the reason do you think? Could you please give me some advice?