[Wien] A basic question regarding using GGA+U approach

[Laurence Marks]

Let me add from an experimental view.

If values of the voltages (formation energies) are known from experiment,
then calculating them and getting "agreement" is criminal murder of
defenceless electrons.

If the values are not known, all one can do is calculate for similar
systems where they are known and adjust the U or hybrid fractions to best
fit energies/atomic positions etc of the known.

Then use these values unchanged for the unknown.

Will the values be right? Nobody on this or any other list can tell you
that. All one can say is that the voltages will be an honest estimate.

🙏

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

On Fri, Feb 11, 2022, 2:11 AM Tran, Fabien <fabien.tran at tuwien.ac.at> wrote:

> There are certainly works reporting calculations on similar systems and
> for similar purpose as yours.
> Just read a few of them to figure out which approach may be appropriate.
>
> ________________________________________
> From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of shamik
> chakrabarti <shamik15041981 at gmail.com>
> Sent: Friday, February 11, 2022 8:34 AM
> To: A Mailing list for WIEN2k users
> Subject: Re: [Wien] A basic question regarding using GGA+U approach
>
> Dear Prof. Xavier,
>  .  .  .  .  .  .  .  .  .  Thank you for your reply. I will follow your
> advice & go for hybrid calculation for all.
>
> With regards,
>
> On Fri, Feb 11, 2022, 12:49 xavier rocquefelte <
> xavier.rocquefelte at univ-rennes1.fr<mailto:
> xavier.rocquefelte at univ-rennes1.fr>> wrote:
>
> Dear Shamik,
>
> To my point of view using the strategy (1) is not correct. I understand
> that B will require a different treatment in ABS2 and pure B phases.
>
> You certainly has no other choice than using hybrid functional for all
> calculations ... and then you will be able to compare to the results of
> strategy (2).
>
> Best Regards
>
> Xavier
>
>
>
> On 11/02/2022 06:40, shamik chakrabarti wrote:
> Dear Wien2k users,
>
>                            I have studied the intercalation of A in BS2 to
> form ABS2. In this calculation, I have used Hubbard U for B in BS2, and in
> ABS2 & I got reasonable voltage.
> However, now I want to study the voltage corresponding to the conversion
> reaction; ABS2 + A =2A2S +B. In this case, B is a metal & hence to simulate
> the voltage
> (1) Should I need to consider the energy value corresponding to GGA+U
> approach applied to ABS2 or,
> (2) Should I need to consider the energy value corresponding to GGA
> approach applied to ABS2
>
> As A & A2S & B have been simulated using GGA.
>
> Looking forward to your reply in this regard.
>
> with regards,
>
> --
> Dr. Shamik Chakrabarti
> Research Fellow
> Department of Physics
> Indian Institute of Technology Patna
> Bihta-801103
> Patna
> Bihar, India
>
>
>
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