[CP2K:2042] Re: optimisation problem of F compound

[Jörg Saßmannshausen]

Dear Axel,

yep, there are plenty in the BASIS_MOLOPT.
However, I was not sure if they are suitable for my problem, hence I did not 
use them. However, I will give it a try.

Thanks for your help!

Jörg


On Donnerstag 23 April 2009 Axel wrote:
> On Apr 23, 5:25 pm, Jörg Saßmannshausen
>
> <jorg.sassm... at strath.ac.uk> wrote:
> > Dear Fawzi,
> >
> > thanks for shedding some light into it (which is easy if it is sunny :-)
> > :-)
> >
> > I am playing around with that problem now for some time. Previously I
> > used BLYP (on a larger system but with the same compound in it) and I got
> > a imaginary frequency which was again movement of the F atom.
> > So I cut down the system and followed Axel's suggestion to use PBE. As I
> > could not find a PBE optimised basis set for F, I tried the two I
> > mentioned. With both I had the imaginary frequencies.
>
> there are plenty of basis set variations for F in BASIS_MOLOPT.
>
> axel.
>
> > I agree with the forces, I think that was what my gutt tried to tell me.
> > I got the feeling the cluster will be very busy tonight ;-)
> >
> > Greetings to Berlin and thanks!
> >
> > Jörg
> >
> > On Donnerstag 23 April 2009 Fawzi Mohamed wrote:
> > > On 23-apr-09, at 22:35, Jörg Saßmannshausen wrote:
> > > > Dear Fawzi,
> > > >
> > > > I actually did:
> > > >
> > > > cutoff energy
> > > > 400  -183.5957955549
> > > > 450  -183.5944280905
> > > > 500  -183.5937679158
> > > > 550  -183.5935371009
> > > > 600  -183.5938000945
> > > >
> > > > one of the things I learned from Rachel at the workshop :-)
> > > >
> > > > For me it looked like that 500 seems to be ok, so I decided to go
> > > > for that
> > > > value.
> > > > However, these values were for the DZVP-ALLELECTRON basis set. I did
> > > > not run a
> > > > test for the aug-DZVP-GTH, simply assuming as I did not change the
> > > > potential
> > > > only the basis set the difference would be not that big?
> > >
> > > normally it is a good assumption to assume that the basis set does not
> > > influence much the cutoff, but switching from GAPW (allelectron) to
> > > GPW does change things, and a lot, gapw does not put the whole density
> > > on the grid, so for it the cutoff is not critical.
> > >
> > > > Or was that a wrong
> > > > assumption? What cutoff would you recommend?
> > >
> > > I haven't calculated with F, but from the high exponent in the basis
> > > (10.7079832847), and also for p functions yo might need more I would
> > > try 800.
> > > Think that you need accurate forces, on *everything* and if you have
> > > just one F looking just at the total energy might be misleading, if
> > > you want to be sure do some steps of MD with HF or something like
> > > that, and look at the energy conservation...
> > >
> > > > Thanks for the prompt reply!
> > >
> > > you are welcome.
> > >
> > > > All the best from a wet Glasgow!
> > >
> > > and greetings from sunny Berlin :)
> > >
> > > Fawzi
> > >
> > > > Jörg
> > > >
> > > > On Donnerstag 23 April 2009 Fawzi Mohamed wrote:
> > > >> I would say that the cutoff of 500 might be too small for the F
> > > >> element. Have you tested the cutoff needed for it?
> > > >>
> > > >> Fawzi
> > > >>
> > > >> On 23-apr-09, at 18:12, Jörg Saßmannshausen wrote:
> > > >>> Dear all,
> > > >>>
> > > >>> I am struggling to optimise a molecular structure with a F atom in
> > > >>> it.
> > > >>> Whereas I manage to get the optimisation converged, the frequency
> > > >>> calculation clearly indicates I am not at the local minimum.
> > > >>> Replacing
> > > >>> the F atom in the molecule with H (and leave everything else the
> > > >>> same)
> > > >>> results in a converged structure. I got the gutt-feeling that the
> > > >>> problem is the basis set / pseudopotential I am using for F. Would
> > > >>> somebody mind to give me a helping hand here?
> > > >>>
> > > >>> I have enclosed the following files:
> > > >>> - mol file of the frequency calculation (so you see what I mean)
> > > >>> - force_eval section
> > > >>> - subsys section
> > > >>> - fluor-geo.inp
> > > >>> - fluor-freq.inp
> > > >>>
> > > >>> I had no problems with the molecule using a different program, so
> > > >>> I am
> > > >>> quite confident about the structure. Note: it is a cation, I left
> > > >>> the
> > > >>> anion out for computational reasons.
> > > >>>
> > > >>> 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.
> > Seehttp://www.gnu.org/philosophy/no-word-attachments.html
>
> 


-- 
*************************************************************
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