[QE-users] CASTEP to QE setup parameters conversions

[Yuvam Bhateja]

I haven't used CASTEP, but from the description you mentioned,
trust_radius_max/min is same. BFGS relaxation converge/finish when total
force and change in total energy is below forc_conv_thr and etot_conv_thr.
Through trust radius you can adjust what can be the max, min and initial
atomic displacement system will make in each BFGS cycle to achieve converge.

On Sun, 15 Nov 2020, 1:37 am Husak Michal, <Michal.Husak at vscht.cz> wrote:

> > First of all, you can find all the information about units of data in
> pw.x input manual.
>
> For conv_thr the units are missing in the manual (but is is probably (a.u.)
>
>
> >Regarding the ecutrho, it is a very important factor for any DFT
> calculation,
>
> ecutrho equivalent is impossible to find in any CASTEP manual mot in
> related materials.
>
> I will ask CASTP developers directly ...
>
>
> According trust_radius_max - there is not clear description in manual how
> it works,  In manual is only written
>
> "
>
> Maximum ionic displacement in the structural relaxation.
> (bfgs only)
> "
>
> Does it mean  BFGS runs until all shifts are less than this criteria ?
>
> ________________________________
> From: users <users-bounces at lists.quantum-espresso.org> on behalf of Yuvam
> Bhateja <yuvamb16 at gmail.com>
> Sent: Saturday, November 14, 2020 8:44:25 PM
> To: Quantum ESPRESSO users Forum
> Subject: Re: [QE-users] CASTEP to QE setup parameters conversions
>
> Hey Michal,
>
> First of all, you can find all the information about units of data in pw.x
> input manual. And yes, you can change the units and use, keep in mind about
> convergence criteria, QE uses total force where as some DFT codes uses max
> force present on a single atom.
>
> Regarding the ecutrho, it is a very important factor for any DFT
> calculation, some programs have different name, for example in SIESTA it is
> meshcuttoff. Please refer to input manual for detailed info of all
> parameters, it can be helpful.
>
> For your geom_disp_tol in CASTEP, you can check trust_radius_(min/max/ini)
> which offers the same purpose.
>
> All the energy units are in Rydberg, as mentioned in manual.
>
> Hope it helps.
> I am also facing similar problems by going from QE to SIESTA.
>
> Keep in touch
>
> Regards
> Yuvam
>
> On Sun, 15 Nov 2020, 12:43 am Husak Michal, <Michal.Husak at vscht.cz<mailto:
> Michal.Husak at vscht.cz>> wrote:
> Hi all
>
>
> I was working a lot with CASTEP last years ...
>
> I want to switch some my projects to  QE + do head to head comparison with
> CASTEP.
>
> I am confused by some selected corresponding setup parameters conversion
>
> (I had handled the rest including input formats conversion myself):
>
>
> QE: etot_conv_thr  (a.u.]
>
> CASTEP: geom_energy_tol (eV/atom)
>
> Should I simply  recalculate eV to a.u. and multiply by number of atoms in
> unit cell ?
>
> Why the definition in QE/CASTEP differs ?
>
>
> QE: forc_conv_thr  (a.u.)
>
> CASTEP: geom_force_tol (eV/angstrem)
>
> I have no idea how to convert this  parameter ....
>
>
> QE: non existing criteria
>
> CASTEP: geom_disp_tol (angstrem) , Maximal atom displacement during a
> cycle ..
>
> Sound like QE does not check this criteria ?
>
>
> QE: ecutrho (Ry), default 4 * ecutwfc
>
> CASTEP: non existing parameter
>
> Any idea why CASTEP does not use this parameter ?
>
>
> QE: conv_thr  , units not found/missing in manual, probably (a.u.) ?
>
> CASTEP: elec_energy_tol (eV/atom)
>
> Should I simply  recalculate eV to a.u. and multiply by number of atoms in
> unit cell ?
>
> Why the definition differs ?
>
>
> Michal Husak
>
> UCT Prague, Department of Solid State Chemistry
>
>
>
>
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