NAMD-QM/MM TUTORIAL: Atoms moving too fast error

From: M. A (
Date: Sun Nov 10 2019 - 03:50:49 CST

 Dear All,

I want to execute QM/MM simulation through QwikMD plugin of VMD. For the
first step, I tried to do NAMD-QM/MM TUTORIAL. First MD and equilibration
were done completely but at the QM/MM part, the minimization step was done
completely but at the annealing part I faced this error:

ERROR: Atom 2575 velocity is 3.75515e+10 -2.86311e+09 9.02613e+09 (limit is
24000, atom 333 of 672 on patch 37 pe 0)
ERROR: Atom 69449 velocity is -2.36584e+09 1.80383e+08 -5.68667e+08 (limit
is 24000, atom 628 of 672 on patch 37 pe 0)
ERROR: Atoms moving too fast; simulation has become unstable (2 atoms on
patch 37 pe 0).

for knowing whether my files have a problem or not even I used ready
minimization output files of the tutorial, but again I faced this error.
I would like to know if anyone knows how to solve this problem?
Could this error be because of my MOPAC file and its installing process?
best regards

Maryam Atabay
Nano Computational Chemistry. Ph.D.
Department of Physics, Sharif University of Technology

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