Dear Dr. Seabra,
Thank you for the suggestion. i think I came across one of your older posts
on the mailing list and did use it. however after 100 steps either the
convergence failure and then vlimit exceed warning and crash. Is it because
of the qmshake=0. This is because I expect the hydrogen bonds between
ligand and receptor to be broken as already seen in MM. The error exists
even at qmshake=1, so cant be because of this.
I am referring also to Dubey et al. (J Biol Phys, 2010) paper. they have
"applied shake on hydrogen atoms". I cant follow this statement. what
parameter to add?
I shall be grateful.
Thank you
On Mon, Nov 24, 2014 at 8:43 PM, Gustavo Seabra <gustavo.seabra.gmail.com>
wrote:
> Hi,
>
> Have you tried changing the defaul setting for DFTB_TELEC? It's not
> something that should be messed with often, but may help in this situation.
> You may try to set it to 100 just until yiu are over this problem, then
> change it back to the default (0).
>
> Hope that helps,
> Gustavo Seabra.
> Em 24/11/2014 03:11, "Ayesha Fatima" <ayeshafatima.69.gmail.com> escreveu:
>
> > Dear all,
> > I am trying to run a qm/mm on a protein-ligand system. I have
> successfully
> > done classical MD without errors. As per information on the mailing list,
> > for qm/mm, i used a well equilibrated .rst file from the classical MM
> > method and was able to do further equilibration with qm/mm using the PM3
> > Hamiltonian. It is in the MD production phase.
> > I want to repeat the same with SCC-DFTB but unfortunately it keeps giving
> > errors in the equilibration phase such as
> >
> > QMMM SCC-DFTB: !!!! ============= WARNING ============= !!!!
> > QMMM SCC-DFTB: Convergence could not be achieved in this step.
> > QMMM SCC-DFTB: The calculation will continue, but energies and
> > QMMM SCC-DFTB: forces for this step will not be accurate.
> >
> > I have looked around on the mailing list and know its a common error. I
> > also tried using the PM3 equilibrated file and trying to further
> > equilibrate it with the SCC-DFTB. But the error still remains. I am
> > attaching my input file. I am sure someone has done it and resolved the
> > issue. Could they share their experience?
> > Thank you
> > Regards
> > Ayesha Fatima
> > PhD candidate UM
> >
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Received on Mon Nov 24 2014 - 05:30:02 PST
