[Pw_forum] global U

Nicola Marzari marzari at MIT.EDU
Mon Aug 10 12:21:10 CEST 2009


ali kazempour wrote:
> 
> Dear users
>  Is it possible to use the hubbard parametr obtained by another code 
> (like wien2k) in espresso or not? is U a global or not?
> thanks


No, it's not, even remotely. Different codes use different 
implementations of U, different definitions (e.g. U-J, for QE), and
even for the same implementation, U would depend on the pseudopotential
used, with fairly large differences if the atomic calculations were
done in different oxidation states (e.g. neutral Fe vs Fe+ vs Fe++ vs
Fe+++).

On the plus side, if you use the appropriate U for each
pseudopotential, you recover broadly similar physical results.

We have a brief summary in the appendix of Kulik/Marzari JCP 2008.

				nicola
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