[Pw_forum] Small U for Co in ZnO for LDA+U (update)

[Nektarios Lathiotakis]

Hi again,

As I wrote previously I have a Co impurity atom in ZnO and
trying to find the right Hubbard-U for Co by fitting to experimental Co-d
projected band  from J. Appl. Phys. 103 07D130 (2008). A typical input file
is in my
previous e-mail.

I played with U_projection_type parameter and:

1) 'ortho-atomic' and 'norm-atomic' agree and give the same optimal U for Co
that is around 4eV. Very reasonable value and no referee would ever object.

2) 'atomic' (the default) gives as optimal U 0.5eV which is much smaller.

In other words the Co-d projected band you get with
U_projection_type='ortho-atomic'
and U_Co = 4 eV is the very close to the band you get with
U_projection_type='atomic'
and U_Co = 0.5 eV.

Why is that difference? The problem with changing the U_projection_type is
that only
atomic supports forces.

Thanks in advance and also to Nicola for his previous reply.
Nektarios



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Dr. Nektarios N. Lathiotakis
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Theoretical and Physical Chemistry Institute
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