[Pw_forum] testing HSE for BCC Fe

[dario rocca]

Ciao Nicola,
I agree that 'time-to-accurate-solution' is the goal. However, when you
have a variable as in Vasp

PRECFOCK= Low | Medium | Fast | Normal | Accurate

that allows you to do a HF calculation in 10 hours if PREFOCK=Low and in an
infinite time if PREFOCK=Accurate, I see the time saving part but the
accuracy can be hardly tested. And it makes also hard to do a comparison of
performance and results with other codes.

Best,

Dario




On Fri, Sep 9, 2016 at 11:55 AM, Nicola Marzari <nicola.marzari at epfl.ch>
wrote:

> On 09/09/2016 11:37, dario rocca wrote:
> > -If you changed the default values of some variables such as Precfock or
> > Nkred in Vasp the computational parameters are not anymore the same in
> > Vasp and QE.
>
>
> Ciao Dario,
>
>
> all true, but at the end what counts for a expert in DFT but not in
> computational implementations is "time-to-accurate-solution".
>
> This latter requires time in itself to establish (i.e. what are the
> parameters
> that give me a converged result - say, for non symmetric configurations,
> with forces that are converged to .XXX eV/A), but for a DFT
> scientist that is a  user of codes, rather than a developer of codes,
> the question above (let's call it TASK "time-to-accurate-solution
> knowing own CPU budget") is a very important one.
>
>                         nic
>
>
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
> Director, National Centre for Competence in Research NCCR MARVEL, EPFL
> http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project
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