[Wien] volume optimization

[Zsolt Rak]

I want to calculate the most accurate bulk energy and the a-priori
information I have are the atomic positions.



On Fri, Mar 1, 2013 at 1:59 PM, Laurence Marks <L-marks at northwestern.edu>wrote:

> My two cents. Both LDA+U and GGA+U are wrong. That said, for f-/d- systems
> they are often better than LDA/GGA for some properties. The question you
> should ask yourself is what property are you trying to measure/predict, and
> what a-priori information (reference state) do you have that can be used?
>
> For instance, if I want to calculate a surface energy then I would tune
> the U to give the most accurate bulk energy treating this as my a-priori
> information; similarly if I wanted to calculate the elastic behavior of a
> defect I would tune to the bulk elastic constants. In my opinion this is
> the only justifiable approach.
>
>
> On Fri, Mar 1, 2013 at 12:47 PM, Zsolt Rak <zsolt.rak at gmail.com> wrote:
>
>>  Dear wien2k users,
>>
>> I am calculating the properties of several f-electron compounds. I would
>> like to ask the users' opinion about the volume optimization in an f- or
>> d-electron system: which way is better (or physically justified), with
>> LDA/GGA or with LDA+U/GGA+U? In my opinion, the LDA+U/GGA+U techniques were
>> developed to correct band energies of localized states, so there is no
>> fundamental physical reason to use LDA+U/GGA+U methods for volume
>> optimization. However, we observe a change in the lattice parameters when
>> we go from LDA/GGA to LDA+U/GGA+U. Also, from a brief search of the
>> literature we found that, in many cases, people tune the Hubbard-U
>> parameter to reproduce the experimental lattice constants.
>> I would appreciate further thoughts and insights into this issue.
>>
>> Thank you,
>> Zs
>>
>
>
>
> --
> 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
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20130301/5416e3c3/attachment.htm>