This could be due to a lot of things. The usual advice is to decrease your
print step (*i.e.* set ntpr = ntwx = 1) and try to visualize what is
happening up until the divergence occurs. Usually you will see a rather
spectacular "explosion" of the QM region due to some specific event.
Just glancing through your input you are turning of bond energies/forces
with hydrogens via SHAKE, including in the QM region. I would strongly
recommend setting "qmshake = 0". It is also rather perilous to do constant
pressure MD with QM/MM unless your system density is stable. I'd recommend
doing the density equilibration step with MM only or else with restraints
on the quantum region.
Regards,
Brian
On Tue, Aug 5, 2014 at 12:23 PM, Muthukumaran R <kumaran.bicpu.edu.in>
wrote:
> Dear amber users,
> I am running QMMM module implemented in AMBER 12. Here is my md.in file.
>
> imin=0,irest=1,ntx=5,
> nstlim=25000,dt=0.001,
> ntc=2,ntf=2,
> cut=10, ntb=2, ntp=1, taup=1.0,
> ntpr=50, ntwx=50,
> ntt=3, gamma_ln=2.0,
> temp0=300.0,
> ifqnt=1,
> /
> &qmmm
> qmmask=":18-20,39-41,60-62",
> qmcharge=-5,
> qm_theory="PM3",
> qmcut=10.0,
> writepdb=1,
> /
>
> After running simulation for 50ps, while extending it to further time
> period ends in following error..
>
> QMMM: WARNING!
> QMMM: Unable to achieve self consistency to the tolerances specified
> QMMM: No convergence in SCF after 1000 steps.
> QMMM: Job will continue with unconverged SCF. Warning energies
> QMMM: and forces for this step will not be accurate.
> QMMM: E = -0.1349E+08 DeltaE = -0.2833E+05 DeltaP = 0.1770E+01
> QMMM: Smallest DeltaE = 0.2069E+03 DeltaP = 0.1570E+01 Step = 73
>
> How to solve this error??
>
> Thanks in advance..
> _______________________________________________
> AMBER mailing list
> AMBER.ambermd.org
> http://lists.ambermd.org/mailman/listinfo/amber
>
--
================================ Current Address =======================
Brian Radak : BioMaPS
Institute for Quantitative Biology
PhD candidate - York Research Group : Rutgers, The State
University of New Jersey
University of Minnesota - Twin Cities : Center for
Integrative Proteomics Room 308
Graduate Program in Chemical Physics : 174 Frelinghuysen Road,
Department of Chemistry : Piscataway, NJ
08854-8066
radak004.umn.edu :
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Received on Tue Aug 05 2014 - 11:30:02 PDT
