[Pw_forum] Fwd: Basic Relax Calculation issues

[Zarah Baiyee]

Thank you both for your responses.

Paolo to clarify, only non-symmetric systems can be relaxed?

Regards

Zarah


On Fri, Feb 28, 2014 at 3:07 PM, Paolo Giannozzi
<paolo.giannozzi at uniud.it>wrote:

> If forces are zero by symmetry, there is nothing to relax
>
> P.
>
> On Fri, 2014-02-28 at 13:06 +0800, Zarah Baiyee wrote:
> > Hi All,
> >
> >
> > I am a new user to Quantum Espresso, therefore this may be a bit
> > trivial but I any help would be very welcome.
> >
> >
> > I am attempting a relax calculation using espresso version 5.0.2, for
> > the geometry optimisation of a perovskite structure. For the input
> > below, the calculation runs, however does not compute any forces and
> > convergence without geometry optimisation to the original structure,
> > with 0 bfgs steps. I am able to perform an expected relaxation if
> > alter the initial atomic positions to asymmetric: (i.e.)  an oxygen
> > molecule from:  O (0.500  0.5  0.0) to O(0.499 0.5 0.0).
> >
> >
> > Please may someone shed some light on to why this is the case, and if
> > there is anything wrong with my input.
> >
> >
> > Thanks
> >
> >
> > Zarah
> > Zbaiyee at gmail.com
> >
> >
> > &CONTROL
> >   calculation  = "relax",
> >   prefix       = "CO",
> >   pseudo_dir   = "/Users/zarahbaiyee/espresso-5.0.2/pseudo",
> >   outdir       = "/Users/zarahbaiyee/tmp",
> >   forc_conv_thr = 1.0D-5
> > /
> > &SYSTEM
> >   ibrav     = 0,
> >   nat       = 5,
> >   ntyp      = 3,
> >   ecutwfc   = 60,
> >   ecutrho   = 420,
> > /
> > &ELECTRONS
> >   conv_thr    = 1.D-7,
> >   mixing_beta = 0.7D0,
> >   electron_maxstep = 400
> > /
> > &IONS
> > /
> > CELL_PARAMETERS bohr
> >  7.60  0.0  0.0
> >  0.0  7.60  0.0
> >  0.0  0.0  7.60
> > ATOMIC_SPECIES
> >  Ba  137.32 Ba.pbe-mt_fhi.UPF
> >  Fe  55.84 Fe.pbe-mt_fhi.UPF
> >  O   15.99 O.pbe-kjpaw.UPF
> > ATOMIC_POSITIONS {crystal}
> > Ba  0.000  0.0  0.0  0 0 0
> > Fe  0.500  0.5  0.5
> > O   0.000  0.5  0.5
> > O   0.500  0.0  0.5
> > O   0.500  0.5  0.0
> >
> > K_POINTS {automatic}
> > 9 9 9 0 0 0
> >
> >
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://pwscf.org/mailman/listinfo/pw_forum
>
> --
> Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20140228/3557b2ee/attachment.html>