[Wannier] Fixed centers?

[Nicolas Lorente]

On 11/11/11 23:51, Sinisa Coh wrote:
> Nicolas Lorente wrote:
>>   Hi,
>>
>> is there anyway of fixing the Wannier centers so they don't move 
>> during the minimization of the spread?
>>
>> This can be useful to identify symmetries or to assign some physical 
>> meaning to certain Wannier functions (we
>> are interested in "defining" an impurity, and sometimes the Wannier 
>> functions move away from the impurity).
>
> Dear Nicolas,
>
> Could you try adding to minimization functional a penalty for Wannier 
> center being away from where you want it to be and then try to 
> minimize that functional?
>
> This would involve some patching of the Wannier code I guess, but it 
> doesn't seem that hard to do.
>
> One problem I see right away is that then you would need to pick an 
> arbitrary constant in front of the penalty and that will introduce new 
> parameter in the problem. Therefore your final Wannier functions will 
> not be unique (unlike max-loc functions which are, more or less).
>
> Best,
> Sinisa
>

OK, I guess you are right and this is the way to go. But, wouldn't it be 
easier just to remove the Wannier center from the list of parameters to 
update when minimizing the spread?


I have not looked into wannier90, I don't know how tough it is to effect 
any changes.

Thanks,

Nicolás

-- 
Nicolás Lorente
Centro de Investigación en Nanociencia y Nanotecnología
Campus de la UAB
E-08193 Bellaterra
Tel. (+34) 935868410

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