[DFTB-Plus-User] MD in liquid water

[Paulo Cesar Piquini]

Dear Christopher and Ben,

I implemented the suggested changes in my input file and it works!
That is great
Thanks a lot.
Do you guys really think there is a bug in the parser?

Yours
Paulo Piquini

On Wed, Oct 7, 2009 at 12:20 PM, Christopher Mark Maupin <
cmaupin at hec.utah.edu> wrote:

> Paulo,
>  I agree with Ben that having N terms in the file may be an issue.  I
> took you file and striped out all the carbons leaving just the water.  I
> then ran the code (with the H and O *.skf files) and the system did not
> converge.  I then noticed you had your Filling = Fermi {
> Temperature[Kelvin] = 0}.  I changed this this to be in agreement with
> the system temp of 300.0 K.  The system then converged in 28 cycles the
> first step, and 10 - 12 cycles for the next few steps.
> When I had question about this issue it was suggested that I use the
> same electronic temperature as MD temp in addition to
> AdaptFillingTemperature = Yes.
> I sure hope this helps
>
> Best wishes,
>
> Mark
> > Hello Paulo,
> >
> > the problem seems to be set of by the nitrogen atoms in the
> > input. Your structure doesn't actually have any N atoms, but there are
> > several places where there are settings for these, which when commented
> > out/removed should cure the problem:
> >
> > TypeNames = {"O" "H" "C"}# "N"}
> >
> > #    N-H = "N-H.skf"
> > #    H-N = "H-N.skf"
> > #    C-N = "C-N.skf"
> > #    N-C = "C-N.skf"
> > #    N-N = "N-N.skf"
> > #    O-N = "O-N.skf"
> > #    N-O = "O-N.skf"
> >
> > #    N = "p"
> >
> > it looks like you have found a bug in the parsing of the input in
> > this case.
> >
> > Regards
> >
> > Ben
> >
> > Paulo Cesar Piquini wrote:
> >
> >> Dear Mark,
> >>
> >> attached you will see the input and the output files of one of my tests.
> >> I played with some variables as timestep and others but the result was
> >> similar or worst.
> >> As you will see, the SCC cycle does not achieve convergence. If one
> >> increases the number of iterations, it goes well until some cycle and
> >> then the problem appears again.
> >> Thanks
> >>
> >> Yours
> >> Paulo
> >>
> >> On Tue, Oct 6, 2009 at 12:19 PM, Christopher Mark Maupin
> >> <cmaupin at hec.utah.edu <mailto:cmaupin at hec.utah.edu>> wrote:
> >>
> >>     DEar Paulo Cesar Piquini,
> >>      I have conducted several liquid water simulations and have not seen
> >>     this issue.  Can you please attach your input file and the output
> file.
> >>
> >>     Best wishes,
> >>
> >>     Mark
> >>
> >>     Paulo Cesar Piquini wrote:
> >>     > Dear users of DFTB+
> >>     >
> >>     > I am a new user of DFTB+ and Iam having difficulties to make the
> SCC
> >>     > cycle to converge when I simulate a liquid water at 300 K.
> >>     > Have someone already performed similar calculations successfully?
> >>     >
> >>     > Thanks
> >>     > Paulo Piquini
> >>     >
> >>     > --
> >>     > Paulo Cesar Piquini
> >>     > Departamento de Física
> >>     > Universidade Federal de Santa Maria
> >>     > 97105-900
> >>     > Santa Maria, RS
> >>     > Brasil
> >>     > Fax: 55 55 3220-8032
> >>     > e-mail: ppiquini at gmail.com <mailto:ppiquini at gmail.com>
> >>     <mailto:ppiquini at gmail.com <mailto:ppiquini at gmail.com>>;
> >>     > ppiquini at smail.ufsm.br <mailto:ppiquini at smail.ufsm.br>
> >>     <mailto:ppiquini at smail.ufsm.br <mailto:ppiquini at smail.ufsm.br>>
> >>     > http://w3.ufsm.br/piquini
> >>     >
> >>     >
> >>
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> >>
> >>
> >> --
> >> Paulo Cesar Piquini
> >> Departamento de Física
> >> Universidade Federal de Santa Maria
> >> 97105-900
> >> Santa Maria, RS
> >> Brasil
> >> Fax: 55 55 3220-8032
> >> e-mail: ppiquini at gmail.com <mailto:ppiquini at gmail.com>;
> >> ppiquini at smail.ufsm.br <mailto:ppiquini at smail.ufsm.br>
> >> http://w3.ufsm.br/piquini
> >>
> >>
> >
> >
>
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-- 
Paulo Cesar Piquini
Departamento de Física
Universidade Federal de Santa Maria
97105-900
Santa Maria, RS
Brasil
Fax: 55 55 3220-8032
e-mail: ppiquini at gmail.com; ppiquini at smail.ufsm.br
http://w3.ufsm.br/piquini
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