[Pw_forum] Born effective charge

[Stefano de Gironcoli]

by searching google "non symmetric born effective charge" I found the 
following reference to a pw_forum previous entry
http://www.democritos.it/pipermail/pw_forum/2006-January/003511.html
that may be of interest.

There is also a reference to a paper Cockayne-Burton PRB 62, 3735 (2000) 
on CaTiO3 that maybe is relevant to your case.

stefano

On 04/07/2011 09:54 AM, mohaddeseh abbasnejad wrote:
> Thanks for your reply.
> I am working on one of the orthorhombic structures of TiO2.
> and it is the first time I have faced this problem.
>
> Yours,
> M. Abbasnejad
> University of Tehran
>
>
> On Thu, Apr 7, 2011 at 12:04 PM, Stefano de Gironcoli<degironc at sissa.it>wrote:
>
>>   what is your system ?
>> born effective charges are not necessarily hermitian although very often
>> they are.
>> stefano
>>
>>
>> On 04/07/2011 09:28 AM, mohaddeseh abbasnejad wrote:
>>
>> Dear all,
>>
>> Trying to calculate the born effective charges of my case, the obtained
>> diagonalized principal values of effective charge tensor have imaginary
>> part.
>>
>> The system has been relaxed carefully using Perdew-Zunger ultrasoft
>> psuedopotentilas by ecutoff=50 (55) Ry, and performing the BZ integration in
>> a 6×6×6 grid with 27 reduced
>> number of k points in the irreducible edge of the 1st BZ.
>>
>> What may cause the problem?
>>
>>
>> Thanks for any comment.
>>
>> Yours,
>> M. Abbasnejad
>> University of Tehran
>>
>>
>>
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