[Pw_forum] DFT+U: about how to get U

[Matteo Cococcioni]

Dear Chao Cao,

Chao Cao wrote:
> Dear Matteo,
>  Thanks for this fast response. I have two more questions.
> I am assuming that by "non-equivalent" you mean non-equivalent site
> instead of non-equivalent type, i.e. if I have two Fe atoms within 1
> unit cell, I'll have to treat them individually, therefore they might
> have different U number?
>
>   

Yes, I meant non equivalent sites. two atoms of the same kind but on 
non-equivalent sites may have different U.

> Also, it looks to me that this method is not restricted to d-electrons,
> and practically it also applies to p and f electrons, am I right?
>
>   

formally it's possible to apply it to p or s electrons. however  the 
LDA+U was designed for localized orbitals.
also with extended orbitals you may need to orthogonalize them because 
you may have significant overlaps bewteen different atoms.
no problem with f states.

Matteo

> Chao Cao
>
> Matteo Cococcioni wrote:
>   
>> Dear Chao Cao,
>>
>> the linear response procedure is repeated only for non-equivalent
>> Hubbard atoms.
>>
>> Regards,
>>
>> Matteo
>>
>>
>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>> Matteo Cococcioni
>> Department of Chemical Engineering and Materials Science
>> University of Minnesota
>> 151 Amundson Hall
>> 421 Washington Av. SE
>> Minneapolis, MN 55455
>> Tel. +1 612 624 9056    Fax +1 612 626 7246
>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>
>>
>> On Oct 16, 2007, at 3:02 PM, Chao Cao wrote:
>>
>>     
>>> Hi there,
>>>   I read about M. Cococcioni's paper and thesis on how to get the U
>>> parameter, and have the following question on mind:
>>>   Does the procedure of perturbing atomic occupation go through every
>>> single atom or just "hubbard" atoms? In the latter case, does the
>>> response matrix chi include elements related with hubbard atoms only (
>>> i.e. chi(m,n) m and n are both hubbard atoms ), or it has to include
>>> everything? If it includes everything, what do we do about elements
>>> related to non-hubbard atoms (maybe set them to 0 (?))?
>>>
>>>   Thanks in advance.
>>>
>>> Chao Cao
>>>
>>> -- 
>>> Chao Cao
>>>
>>> Quantum Theory Project and Department of Physics
>>> University of Florida, Gainesville, FL 32611
>>> U.S.A.
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org <mailto:Pw_forum at pwscf.org>
>>> http://www.democritos.it/mailman/listinfo/pw_forum
>>>       
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>>   
>>     
>
>
>   

-------------- next part --------------
A non-text attachment was scrubbed...
Name: matteo.vcf
Type: text/x-vcard
Size: 294 bytes
Desc: not available
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20071017/c0ce1562/attachment.vcf>