[Pw_forum] global U

[Nicola Marzari]

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
-- 
---------------------------------------------------------------------
Prof Nicola Marzari   Department of Materials Science and Engineering
13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu