[Pw_forum] U calculation in LDA+U

[Stefano de Gironcoli]

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
>
>
>
>
>
>
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