[Pw_forum] about Hubbard_alpha

[Stefano Fabris]

Dear Ruijuan,

the value of "Hubbard_alpha" has to be zero in your routine LDA+U
calculations. That variable is used ONLY when you want to estimate the
value of the parameter U from a set of calculations. This is done by
adding to the effective potential a local perturbation (proportional
to the value of "hubbard_alpha") acting on the localized states of a
specific site and then calculating the resulting changes in the
occupancies of the localized states. The procedure is described in the
following paper (M Cococcioni and S de Gironcoli, cond-mat/0405160),
and in the PhD thesis of Matteo Cococcioni
(http://www.sissa.it/cm/phd.php).

Best wishes,
				Stefano


On Sun, 17 Oct 2004, Ruijuan Xiao wrote:

> Dear all,
>  When I use the LDA+U in the PWSCF, I found that there is a
> parameter which is called "Hubbard_alpha". I can't find its meaning
> in the help of PWSCF. Can you tell me how to set this parameter?  
> Thank you very much.
>  
> Best regards,
>  
> Sincerely,
> Ruijuan Xiao
> 
> 
> 		
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Stefano Fabris                               fabris at democritos.it
INFM DEMOCRITOS - SISSA                      tel: +39 040 3787405
via Beirut 2-4, I-34014 Trieste, Italy       fax: +39 040 3787528
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