[Pw_forum] benzoic acid structure optimization

[matt reish]

Thanks for the reply, seemed to be going way too fast for what I had read I
that I should expect. Any thoughts on what would be more reasonable cutoffs
for wavefunction and density? Would it be reasonable to try to attain a
useable result on a "cluster" using 8 processors?

Cheers,

Matt

On Wed, May 2, 2012 at 3:02 PM, Axel Kohlmeyer <akohlmey at gmail.com> wrote:

> On Tue, May 1, 2012 at 10:53 PM, matt reish <reishme04 at gmail.com> wrote:
> > Hi PW list,
> >
> > I am working with Quantum Espresso (v4.3.2.1) in the hopes of attaining
> > Raman phonon frequencies of a benzoic acid crystal. I attained the
> optimized
> > output geometry from a CASTEP calculation in the supplemental material
> of a
> > paper. This geometry was used by the authors to calculate accurate IR
> phonon
> > frequencies. I used a 'relax' calculation in Quantum Espresso on the
> > optimized geometry but this led to large shifts in the atomic positions
> in
> > the lattice and unreasonable structures for the molecules in the lattice
> > after finding the optimized structure. My question is does anyone have a
> > some experience calculating organic crystals in Quantum Espresso that
> could
> > give me some tips?
>
>
> matt,
>
> you are using a *ridiculously* low wavefunction
> and density cutoff, that means your basis set
> is *far* too small. unphysical results are the
> logical consequence.
>
> axel.
>
>
> >
> > Here is my input file minus the atomic posititions:
> >
> > &CONTROL
> >                        title = 'benzacidscftest' ,
> >                  calculation = 'relax' ,
> >                 restart_mode = 'from_scratch' ,
> >                       outdir = '/home/mreish/tmp/' ,
> >                   pseudo_dir = '/usr/share/espresso/pseudo/' ,
> >                       prefix = 'batest5' ,
> >                      disk_io = 'default' ,
> >                        nstep = 600 ,
> >  /
> >  &SYSTEM
> >                        ibrav = 12,
> >                            A = 5.4996 ,
> >                            B = 5.1283 ,
> >                            C = 21.950 ,
> >                        cosAB = 0 ,
> >                        cosAC = -.128276341 ,
> >                        cosBC = 0 ,
> >                          nat = 60,
> >                         ntyp = 3,
> >                      ecutwfc = 5 ,
> >                      ecutrho = 40 ,
> >  /
> >  &ELECTRONS
> >             electron_maxstep = 200,
> >                     conv_thr = 1.0d-11 ,
> >  /
> >  &IONS
> >  /
> > ATOMIC_SPECIES
> >     C   12.01000  C.pbe-rrkjus.UPF
> >     O   16.00000  O.pbe-rrkjus.UPF
> >     H    1.00000  H.pbe-rrkjus.UPF
> > ATOMIC_POSITIONS angstrom
> >
> > K_POINTS automatic
> >   1 1 1   1 1 1
> >
> >
> > Cheers,
> >
> > Matthew Reish
> > University of Otago
> > Dunedin
> > New Zealand
> >
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >
>
>
>
> --
> Dr. Axel Kohlmeyer
> akohlmey at gmail.com  http://goo.gl/1wk0
>
> College of Science and Technology
> Temple University, Philadelphia PA, USA.
>
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