[Wien] A basic question about GGA+U approach

[Laurence Marks]

A general comment: you may want to use the onsite exact-exchange instead of
LDA/GGA+U. It is less sensitive to the precise environment. However, in my
experience this (and LDA/GGA+U) is better just of d-orbitals, and less
effective for O p levels.

On Tue, Jun 26, 2012 at 10:47 AM, Shamik Chakrabarti <shamikiitkgp at gmail.com
> wrote:

>  Dear Haranath Ghosh,
>
>           Yes U can be used for p orbital of oxygen...but what value of U
> you are going to use that depends on the system and the problem you are
> studied.....& also what error you are getting??...that is not clear from
> your mail
>
>  with regards,
>
> On Tue, Jun 26, 2012 at 6:48 PM, Haranath Ghosh <ghoshharanath at yahoo.com>wrote:
>
>>   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<http://us.mc1606.mail.yahoo.com/mc/compose?to=pblaha@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
>>
>>
>>  ______________________________**_________________
>> Wien mailing list
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>> http://zeus.theochem.tuwien.**ac.at/mailman/listinfo/wien<http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien>
>>
>>
>> --
>> 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
>>
>>  -----Inline Attachment Follows-----
>>
>>
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>>
>
>
>  --
> Shamik Chakrabarti
> Senior Research Fellow
> Dept. of Physics & Meteorology
> Material Processing & Solid State Ionics Lab
> IIT Kharagpur
> Kharagpur 721302
> INDIA
>



-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu 1-847-491-3996
"Research is to see what everybody else has seen, and to think what nobody
else has thought"
Albert Szent-Gyorgi
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