[Wien] Questions about LDA+U calculations

[Stefaan Cottenier]

>1. Is it possible to include U and J for both f-  and d-orbitals?
>   For rare earth compounds, it seems that both f- and d-orbitals are 
>actually important near the Fermi level. I have tried to include d- and 
>f- orbitals in
>   case.inorb and case.indm, but the program always breaks down either 
>when reading *.vorbup  or when reading *.dmatup.
>  
>
Don't do that. LDA+U should be applied to the orbital that has strong 
electron-electron correlations, and in the case of rare earths these are 
clearly the 4f-orbitals only. The 5d is hardly occupied, and is too much 
extended in space to show strong correlation.

>2. For the same U and J values, will three LDA+U options, i.e.
>       nsic=0..AMF, 1..SIC, 2..HFM
>give significantly different results?
>  
>
Depends on what you mean with 'significant'. For sure there will be 
differences, but in my experience they are small for rare earths. The 
usersguide recommends SIC for rare earths (page 78, sec. 7.2).

Stefaan


Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm