[Wien] confusion about the caculation U in LDA+U method

[Stefaan Cottenier]

>In addition, whether the U is depend on the overall molecule electron system,or just the transition mental atom. Which I mean I found the value of U of the transation metal in other system, can I use it in my own system?
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For transition metals, U depends both on the type of atom to which it is
applied and on the environment of that atom. For lanthanides, the
environment is much less important.

>Farther more, is it a reasonable way I add this U to the GGA exchange potential? Or does the so called GGA+U using a different U?
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GGA+U needs a different, smaller U -- GGA has already some extra
correlation 'built in'. If I'm not mistaken, a rule of thumb is to
subtract 0.2-0.3 Ry from the LDA value of U..

Stefaan


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