Hi Gabriel,
If your SCF does not converge, the forces will be meaningless and consequently the optimized geometry and/or MD trajectory. Since you say that DFTB does not suffer from this problem it might be specific to the AM1D implementation. Did you try other NDDO type Hamiltonians that support the elements of your QM region? Does the SCF converge with AM1/PM3/PM6 and do you get a reasonable geometry?
All the best,
Andy
On May 3, 2012, at 3:10 PM, Gabriel Jara wrote:
> Hi,
>
> I am running qmmm calculations using AM1D. The system of interest is a
> kinase with one atp molecule and two magnesium cations within a protein
> environment. The QM region includes the atp molecule, magnesium cations and
> side chain of a threonine, a aspartic and a lysine.
>
> Both in optimization and MD each atom of the QM region starts to move away
> from each other. When I did this same thing using DFTB that problem did not
> happen.
>
> Also, the mdout show the next message in both optimization and MD.
>
> QMMM: WARNING!
> QMMM: Unable to achieve self consistency to the tolerances specified
> QMMM: No convergence in SCF after 2000 steps.
> QMMM: Job will continue with unconverged SCF. Warning energies
> QMMM: and forces for this step will not be accurate.
> QMMM: E = -0.8693E+06 DeltaE = -0.5769E+03 DeltaP = 0.1544E+01
> QMMM: Smallest DeltaE = 0.3633E-01 DeltaP = 0.1045E+01 Step = 210
>
> In the optimization this message is not showed if i use the keywords
> ndiis_attempts=50 ndiis_matrices=10. However the QM structure continue
> destroying itself in the optimization.
>
> I attach the mdin file for the optimization.
>
> Thanks in advance.
>
> Gabriel
>
>
> --
> Dr. Gabriel E. Jara
> INQUIMAE - CONICET
> Facultad de Ciencias Exactas y Naturales
> Universidad de Buenos Aires
>
>
>
>
> --
> Dr. Gabriel E. Jara
> INFIQC - CONICET
> Departamento de Química Orgánica
> Facultad de Ciencias Químicas
> Universidad Nacional de Córdoba
> Tel: ++54-351-4334170/4173 int. 132
> Fax: ++54-351-4333030
> X5000HUA - Córdoba -Argentina
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--
Dr. Andreas W. Goetz
Assistant Project Scientist
San Diego Supercomputer Center
Tel : +1-858-822-4771
Email: agoetz.sdsc.edu
Web : www.awgoetz.de
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Received on Mon May 07 2012 - 14:00:03 PDT
