failure in RATTLE algorithm using the adaptive biasing force method

From: steve.kaminski_at_mail.tu-berlin.de
Date: Tue Nov 11 2008 - 13:43:51 CST

Dear all.

My aim is to calculate a PMF of a certain molecule as a function of a
dihedral angle. Therefore, I use the adaptive biasing force method. As
long as I scan the complete dihedral space (xiMin=-180 / xiMax=180)
the calculations run without problems. But in my case I just want to
scan a reduced space, so if I change the values e.g. of xiMin to -100
or any other value, I get immediately the following error message from
NAMD:

  Warning: Constraint failure in RATTLE algorithm for atom 19
  Warning: Constraint failure in RATTLE algorithm for atom 22

If I turn off rigidBonds in the NAMD config-file I receive the
following error:

ERROR: Atom 20 velocity is 1050.76 -3548.3 -5428.46 (limit is 5000)
ERROR: Atoms moving too fast; simulation has become unstable.
ERROR: Exiting prematurely.

Thank you very much in advance for your suggestions.

Steve

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