[DFTB-Plus-User] SCC does not converge.
Dawid Grabarek
dawid.grabarek at pwr.edu.pl
Thu Feb 18 19:43:02 CET 2016
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
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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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