Re: [Pw_forum] Negative Polarization !!!

[Mojtaba Mirseraji]

Dear Mostafa

Thanks a lot



On 5/12/15, Mostafa Youssef  wrote:
> Hi Mojtaba,
>
> Polarization is a vector, so negative or positive just indicate its
> direction. So no worries about negative polarization. But in periodic
> boundary conditions you may still need to add (subtract) multiples of the
> polarization quantum in order to get the "reasonable" value of the
> spontaneous polarization of the material.
>
> A favorite of mine which go over some of these difficulties is this  paper:
>
> http://journals.aps.org/prb/abstract/10.1103/PhysRevB.71.014113
>
>
> Mostafa Youssef
> MIT
>
>
>
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Re: [Pw_forum] Negative Polarization !!!

[Mostafa Youssef]

Hi Mojtaba,

Polarization is a vector, so negative or positive just indicate its direction. 
So no worries about negative polarization. But in periodic boundary conditions 
you may still need to add (subtract) multiples of the polarization quantum in 
order to get the "reasonable" value of the spontaneous polarization of the 
material.

A favorite of mine which go over some of these difficulties is this  paper:

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.71.014113


Mostafa Youssef
MIT


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[Pw_forum] Negative Polarization !!!

[Mojtaba Mirseraji]

Dear All

If we have a negative total polarization (by nscf+lberry),has it meaning?
This happens, for example, in strain study of tetragonal perovskites.
if it has meaning, what does it mean, physically?
I have some problem with negative polarization 

Regards

Mojtaba Mirseraji
Ph.D. Candidate
Theoretical Condensed Matter Physics
Arak University
I.R.IRAN
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