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[Anurag Chaudhry <anuragchaudhry@yahoo.co.uk>]

Hello Everyone,

I would like to know your suggestions for the following issue.  

Regarding little I know about LDA+U method from different publications in literature I have seen people use a particular U correction for an element from a value published earlier in literature.  Like I am interested in LDA+U (or GGA+U) calculations for Europium (Eu2+) and I have seen values like U-J = 6eV (Dudarev approach) or close to this number.  These numbers are from publications where Eu compounds like EuO, EuS, ... etc have been studied. 

I am interested in compounds where Eu2+ is a substitutional impurity in inorganic compounds of Ba and Sr.  So I am studying supercells of these compounds (~40-50 atoms) with one Ba/Sr replaced by a Eu. In such a situation what should be the value of U correction for Eu 4f electrons ?  I have tried using a 6eV (=U-J) but the DOS plots show that the 4f electrons are inside the valence band.  This we know from experiments (for a particular compound BaI2) is not true.  Unfortunately I do not have any other information from the experiments.

Is there a way to calculate/estimate the U parameter ?  

Thank you very much for your help.

I realize the question may not be completely relevant to the forum and apologize for it.

regards,

Anurag

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