[Wien] A basic question about GGA+U approach

[Haranath Ghosh]

Dear experienced Users and developer Wien2k,
 
 Is it possible to use U value for Oxygens with l=1 orbitals. I always get error. Thanks for your response.
 
with best regards, Haranath Ghosh

--- On Tue, 6/26/12, shamik chakrabarti <shamikphy at gmail.com> wrote:


From: shamik chakrabarti <shamikphy at gmail.com>
Subject: Re: [Wien] A basic question about GGA+U approach
To: "A Mailing list for WIEN2k users" <wien at zeus.theochem.tuwien.ac.at>
Date: Tuesday, June 26, 2012, 6:37 PM


Dear Prof. Peter Blaha,


            Thank you very much for your reply. I got my answer.


with best regards,


On Tue, Jun 26, 2012 at 11:19 AM, Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:

Yes, U depends on the type of atom, but of course also on the specific compound.
For metallic Fe the U should be in the range of 0-2 eV at most, for some insulating compound with very localized states, it may go up to even 4-6 (maybe even 8) eV.

Am 26.06.2012 06:42, schrieb shamik chakrabarti:


Dear wien2k users,

       We generally choose the value of U by fitting it with
experimental band gap or by calculating it through linear response
method. Now my question is that whether U is element specific or depends
on the composite in which the element reside? (*if I consider same

magnetic configuration for all the composites I am referring here...as
antiferromagntism do produce a band gap even without applying any U*)


To make it more clear, say for Fe d, I have seen in literature, people
have used U=4.5 to 5 eV......in some of our calculation we have even
used U=6 eV for Fe d to obtain better electronic structure having closer
match with experimental observation. Hence it looks that U for Fe d
orbital can have value ranging from 4.5-6 eV...& that mean U is not
element specific rather it depends on the composite in which the element
exist (I again want to insist that if I consider same magnetic
configuration for all the composites). Am I right?

with regards,

--
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics & Meteorology
Material Processing & Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA


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-- 
Peter Blaha
Inst.Materials Chemistry
TU Vienna
Getreidemarkt 9
A-1060 Vienna
Austria
+43-1-5880115671


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-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics & Meteorology
Material Processing & Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA

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