[Wien] Why unit cell energy is same on increasing pressure ? and Band gap problem with pressure.

[Zaid]

Sir, Energies are calculated with GGA only. The second issue is seperate,
which is about energy Band Gaps. Band gaps are calculated with mBJ-GGA and
GGA+U. Still not clear about these anomalic trends in first and second
issue ? Thank you for your kind attention.


On Fri, Jun 21, 2013 at 11:51 PM, Stefaan Cottenier <
Stefaan.Cottenier at ugent.be> wrote:

>
>  Your lowest energy is at 10GPa,
>>
>
> Ups.. I did not notice that, as I compared only the 0 and 30 GPa cases.
>
> My guess about what has happened: GGA was used to determine the 4 volumes.
> While the table shows not the GGA energies but rather the GGA+U energies.
>
> If that guess is correct, then the advice is: be consistent and determine
> the pressure at the same level of theory as you use for the band gap. This
> holds at least for GGA+U, not as much for mBJ as the latter is not a
> functional (no forces = no internal positions).
>
> Stefaan
>
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