[Wien] structure optimization using LAD+U

[Stefaan Cottenier]

> I am working on the magnetic properties of rare earth–iron   
> compounds. I have a question in structure optimization.
> How to set the U and J parameters when using LDA+U method, since U   
> and J can’t be calculated by ab initio way? So I just set U=J=0. If   
> it is reasonable, then is it necessary to runsp_lapw with ‘–orb’?

With U=J=0, you are doing a LDA calculation... That will not produce  
good results for rare earth-iron compounds.

Check the literature to see what other people found to be meaningful  
U-values for rare earth-iron systems, for instance

Torumba et al., PRB 74, 014409 (2006),  
http://link.aps.org/abstract/PRB/v74/e014409
Torumba et al., PRB 77, 155101 (2008),  
http://link.aps.org/abstract/PRB/v77/e085123
Tran et al., PRB 77, 85123 (2008),  
http://link.aps.org/abstract/PRB/v77/e155101

and references therein. If these U-values do not produce good results  
for your compounds, modify them (slightly) and see whether that  
improves the situation for you.

Stefaan


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