[Pw_forum] U calculation in LDA+U

[Peng Chen]

Thanks  stefano and Burak.

If space group matters, then the 3 types will be A, B and O.

On Tue, Jul 10, 2012 at 9:37 AM, Burak Himmetoglu <himm0013 at umn.edu> wrote:

> Hi Peng,
>
> r.x assigns the values of the response matrices only by considering the
> distance between atoms and whether they have the same spin and type or not.
> This information has to be given by the user in the positions file
> "filepos" read by &input_mat. If B(1) and B(2) are different types
> (e.g. crystallographically) you should perturb them separately, as you
> outlined in the procedure, and make sure that ntyp=3 (type 1 is B(1), type
> 2 is B(2) and type 3 is O) in the namelist &input_mat that goes into r.x
>
> Best regards,
>
> Burak
>
>
> On Tue, Jul 10, 2012 at 1:45 AM, Stefano de Gironcoli <degironc at sissa.it>wrote:
>
>>  I don't know the details of r.x code but I think that, physically, what
>> matters is the two atoms are crystallographically equivalent or not
>> .therefore I think space group symmetry is the relevant one.
>>
>> stefano
>>
>>
>> On 07/10/2012 05:54 AM, Peng Chen wrote:
>>
>> Dear All,
>>
>> In the calculation of U, how can we determine the equivalence of the ions,
>> by site symmetry or space group symmetry?
>> E.g  ABO3, B ions has 2 different site symmetries (B(1) B(2)). Shall we run
>> calculation on perturbing B(1) and B(2) ions or  just a B ion?
>>
>>  In order to find U in B  ions, I tried to run calculation with perturbing
>> just on B, and r.x gave some errors that it needs to read more data.
>> So I guess it needs the perturbed data from other atoms. Shall I use the
>> procedures listed below?
>> 1. run scf calculation with Hubbard_U(i)= 1.d-20
>> 2. run scf with perturbing on an A ion
>> 3.   run scf with perturbing on a B(1) ion
>> 4.   run scf with perturbing on a B(2) ion
>> 5.   run scf with perturbing on an O ion
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing listPw_forum at pwscf.orghttp://www.democritos.it/mailman/listinfo/pw_forum
>>
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>


-- 
  Best Regards.
        Peng
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20120710/c8eb7a6a/attachment.html>