[CP2K:1965] Re: Geometry Optimisation / Frequency (general question)
Jörg Saßmannshausen
jorg.sassm... at strath.ac.uk
Mon Apr 6 18:10:56 UTC 2009
Hi Theo,
copy&pasta mistake:
first (for geo-opt and first frequency):
EPS_SCF 1.0E-8
and then (only for the second frequency):
EPS_SCF 1.0E-9
And yes, you were right in some respect, I originally started that all off
with EPS_SCF 1.0E-6 but right now I am using EPS_SCF 1.0E-8 right from the
beginning as with higher values I had problems to find the minimum (i.e. more
neg. frequencies).
The snip from the output file for the geo-opt:
eps_scf: 1.00E-08
eps_scf_history: 0.00E+00
eps_diis: 1.00E-01
eps_eigval: 1.00E-05
--------------------------------------------------------
p_mix: 0.40
G-space mixing a: 1.00
G-space mixing b: 0.00
work_syevx: 1.00
level_shift [a.u.]: 0.00
and of the freq.inp:
&VIBRATIONAL_ANALYSIS
NPROC_REP 4
DX 0.001
&PRINT
&PROGRAM_RUN_INFO ON
&END
&MOLDEN_VIB
&END
&END
&END
I remembered from your last reply that DX 0.001 is ok, so I did not mess
around with that one.
One other question, number of replicas is the number of the CPUs used? Or did
I get that wrong?
Thanks for the quick reply Theo!
On a more personal side, I hope that nobody you know was effected by the earth
quake today in Italy!
All the best!
Jörg
On Montag 06 April 2009 Teodoro Laino wrote:
> Hi Jörg,
>
> I'm a bit confused:
> > I have managed to get a converged geometry with these parameters:
> > &GEO_OPT
> > MINIMIZER BFGS
> > MAX_ITER 300
> > MAX_DR 3.00E-4
> > RMS_DR 1.50E-4
> > MAX_FORCE 4.50E-5
> > RMS_FORCE 3.00E-5
> > &BFGS
> > &END
> > &END GEO_OPT
> >
> > and
> > EPS_SCF 1.0E-8
>
> so you used 1.0E-8 for GEO_OPT. and then you did with the same EPS_SCF
> the frequency analysis and you got
> a neg. freq. then you decreased the value to 1.0E-8 (which is the same
> as before :-) ) and it solved your issue..
> well.. then you were just lucky and you may have had a problem with the
> interaction of neutrinos with your CPU ;-).
>
> I suspect your first EPS_SCF was the default 1.0E-6. right?
>
> in any case (general rule) if the numerical frequencies are computed by
> finite differences of course you need to
> be careful, especially for low-frequencies. Infact, depending on DX and
> EPS_SCF you may just observe numerical
> noise for small frequencies.
> You did it right then!
>
> Cheers
> Teo
>
> > Using the same EPS_SCF 1.0E-8 for the frequency analysis, I get one neg.
> > freq. at -42.76 1/cm. However, as I remembered from the ADF program, it
> > might be actually beneficial to use a tighter criterion for the numerical
> > frequency analysis, so I decreased the value to EPS_SCF 1.0E-8 and loo!
> > now that neg. frequency has gone.
> >
> > Is that generally a good idea to run the frequency calculation a bit
> > tighter than the geometry optimisation or was I just lucky?
> >
> > I just try to get the grips of the program, hence the question.
> >
> > Thanks for your help!
> >
> > Jörg
>
>
--
*************************************************************
Jörg Saßmannshausen
Research Fellow
University of Strathclyde
Department of Pure and Applied Chemistry
295 Cathedral St.
Glasgow
G1 1XL
email: jorg.sassm... at strath.ac.uk
web: http://sassy.formativ.net
Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html
More information about the CP2K-user
mailing list