[DFTB-Plus-User] SCC does not converge.

Dawid Grabarek dawid.grabarek at pwr.edu.pl
Thu Feb 18 20:42:41 CET 2016


Dear Nir,

I forgot that by default temperature is given in energy units... .
Now when I use 
Temperature [K] = 300.0

everything seems fine.

Regards,
Dawid Grabarek

----- oryginalna wiadomość -----
od: "Goldman, Nir" <goldman14 at llnl.gov>
data: czwartek, luty 18, 2016 20:33
temat: Re: [DFTB-Plus-User] SCC does not converge.
do: User list for DFTB+ related questions <dftb-plus-user at mailman.zfn.uni-bremen.de>


    | 

 
> Dear Dawid,> > 
 > I was able to run a number of geometry optimization steps on the larger system you sent earlier (chromo-0.5.gen) by including the following in your input file:> > 
  >   Filling = Fermi {
 >     Temperature [Kelvin] = 300.0
 >   }
 > 
 
 > I also changed the SCC convergence to 1e-6, which likely helped speed things up.
 > 
 
 > Setting the electronic temperature to a non-zero value allows for the Mermin functional to be calculated, which essentially “smears" the electrons to excited states by computing fractional occupancies for the system according to the  Fermi-Dirac distribution.  This can effect can be very important to systems with molecular ions, for example, which can exhibit thermal electronic excitations even at relatively low temperature. 
 > 
 
 > Hope that helps,
 > 
 
 > Nir
 > > 
  >  > From: <dftb-plus-user-bounces at mailman.zfn.uni-bremen.de> on behalf of Dawid Grabarek <dawid.grabarek at pwr.edu.pl>
 > Reply-To: User list for DFTB+ related questions <dftb-plus-user at mailman.zfn.uni-bremen.de>
 > Date: Thursday, February 18, 2016 at 10:43 AM
 > To: User list for DFTB+ related questions <dftb-plus-user at mailman.zfn.uni-bremen.de>
 > Subject: Re: [DFTB-Plus-User] SCC does not converge.
  > > 
   >  > > Dear Ben,
 > 
>  Unfortunately, my happiness came too early... . As the optimization proceeds 
>  my system blows up. All bonds break down and atoms just fly into space... .
>  I have noticed that all oxygen and sulfur atoms get charges equal ca. +1.5 
>  for the "optimized" structure. In fact, the breakdown of all of my systems 
>  begins just after first optimization step. What would you suggest? 
>  Different initial charges?
 > 
>  Best regards,
>  Dawid Grabarek
 > 
>  ----- oryginalna wiadomość -----
>  od: Ben Hourahine <benjamin.hourahine at strath.ac.uk>
>  data: czwartek, luty 18, 2016 16:29
>  temat: Re: [DFTB-Plus-User] SCC does not converge.
>  do: dftb-plus-user at mailman.zfn.uni-bremen.de
 > 
  
  -----------------------------------------------------------


> _______________________________________________>  > DFTB-Plus-User mailing list>  > DFTB-Plus-User at mailman.zfn.uni-bremen.de>  > https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb->  > plus-user> >  ------->  Dawid Grabarek, M.Sc.>  Wroclaw University of Technology>  Faculty of Chemistry>  Advanced Materials Modelling and Engineering Group> > 
 >  >  > > 
  >  > --  > Nir Goldman > Material Sciences Division, PLS > Lawrence Livermore National Laboratory > P.O. Box 808, L-288 > Livermore, CA 94551-0808 > Phone: (925) 422-3994 > Fax: (925) 422-2382 > https://pls.llnl.gov/people/staff-bios/msd/goldman-n     |-----------------------------------------------------------

> _______________________________________________
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-------
Dawid Grabarek, M.Sc.
Wroclaw University of Technology
Faculty of Chemistry
Advanced Materials Modelling and Engineering Group-----------------------------------------------------------
       |  
> > Hello Dawid,
 > > 
 > > have you tried a finite electronic temperature (this can really help with self consistency)?
 > > The attached example was at 0 Kelvin, I'd suggest something like room temperature as a first test.
 > > 
 > > Also the SCC tollerance you are using is quite small (try the default value, unless there is a good reason otherwise).
 > > 
 > > Regards
 > > 
 > > Ben
 > > 
 
> > > > On 07/02/16 21:11, Dawid Grabarek wrote:
 > > Dear DFTB+ Experts,
 > > 
 > > I want to perform geometry optimization of a system consisting of increasing 
 > > number of amino acid residues.
 > > I have managed to successfully perform optimization for system up to 
 > > 1870 atoms, using non-SCC DFTB approach.
 > > However when I want to use SCC-DFTB3 for system larger than 460 atoms, 
 > > the charges do not converge even after a few thousand iterations. The iteration 
 > > does not proceed in fact.
 > > I attach part of my output file:
 > > 
 > >  9976   -0.21529827E+03   -0.13123659E+02    0.53106709E+01
 > >  9977   -0.17459612E+03    0.40702148E+02    0.53210677E+01
 > >  9978   -0.20103686E+03   -0.26440744E+02    0.53230816E+01
 > >  9979   -0.24096058E+03   -0.39923717E+02    0.53269557E+01
 > >  9980   -0.19704089E+03    0.43919692E+02    0.53385778E+01
 > >  9981   -0.21818849E+03   -0.21147597E+02    0.53345550E+01
 > >  9982   -0.25301554E+03   -0.34827052E+02    0.53358740E+01
 > >  9983   -0.27482831E+03   -0.21812768E+02    0.53316452E+01
 > >  9984   -0.29608303E+03   -0.21254728E+02    0.53454981E+01
 > >  9985   -0.26626843E+03    0.29814602E+02    0.53557124E+01
 > >  9986   -0.29473653E+03   -0.28468098E+02    0.53569507E+01
 > >  9987   -0.25516950E+03    0.39567029E+02    0.53763278E+01
 > >  9988   -0.28536057E+03   -0.30191072E+02    0.53798582E+01
 > >  9989   -0.28895556E+03   -0.35949882E+01    0.53806192E+01
 > >  9990   -0.22896112E+03    0.59994443E+02    0.53836906E+01
 > >  9991   -0.22485550E+03    0.41056157E+01    0.53812648E+01
 > >  9992   -0.22164301E+03    0.32124948E+01    0.53759401E+01
 > >  9993   -0.16929036E+03    0.52352651E+02    0.53873225E+01
 > >  9994   -0.19352833E+03   -0.24237970E+02    0.53825003E+01
 > >  9995   -0.16294863E+03    0.30579698E+02    0.53834931E+01
 > >  9996   -0.11288863E+03    0.50060003E+02    0.53970748E+01
 > >  9997   -0.10136437E+03    0.11524262E+02    0.53984882E+01
 > >  9998   -0.10537121E+03   -0.40068449E+01    0.53984460E+01
 > >  9999   -0.84099319E+02    0.21271891E+02    0.53857706E+01
 > > 10000   -0.76159647E+02    0.79396717E+01    0.53785016E+01
 > >  
 > >  Total Energy:                     -66.7997002259 H
 > >  Total Mermin free energy:         -66.7997002259 H
 > > ERROR!
 > > -> SCC is NOT converged, maximal SCC iterations exceeded
 > > 
 > > I know that going up to 10 000 is crazy but just wanted to see what will happen.
 > > 
 > > Anyway, I also attach two input files for systems for which I cannot 
 > > reach the SCC convergence. What is more I also attach a PDF file which contains 
 > > various parameters combination that I used to check whether changing 
 > > parameters and Mixer will allow to reach convergence. 
 > > I did that based on what I read in paper by V. Eyert (Journal of
 > > Computational Physics, 124, 271-285, 1996).
 > > 
 > > Best wishes,
 > > 
 > > Dawid Grabarek
 > > 
 > > 
 > > 
 > > -------
 > > Dawid Grabarek, M.Sc.
 > > Wroclaw University of Technology
 > > Faculty of Chemistry
 > > Advanced Materials Modelling and Engineering Group
 > > 
  >  > 
 > > _______________________________________________ > DFTB-Plus-User mailing list > DFTB-Plus-User at mailman.zfn.uni-bremen.de https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user  > > --  >       Dr. B. Hourahine, SUPA, Department of Physics, >     University of Strathclyde, John Anderson Building, >             107 Rottenrow, Glasgow G4 0NG, UK. >     +44 141 548 2325, benjamin.hourahine at strath.ac.uk >  > 2013/4 THE Awards Entrepreneurial University of the Year >       2012/13 THE Awards UK University of the Year >  >    The University of Strathclyde is a charitable body, >         registered in Scotland, number SC015263  | -----------------------------------------------------------
      
 
 
  




 





      

  







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