[DFTB-Plus-User] MD in liquid water

[Christopher Mark Maupin]

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
>>
>>     
>
>