The RD-SHAKE algorithm for bond
constraints is iterative. If the
maximum number of permitted iterations is exceeded, the program
terminates. Possible causes include: a bad starting configuration; too
large a time step used; incorrect force field specification; too high
a temperature; inconsistent constraints involving shared atoms etc.
Action:
Corrective action depends on
the cause. It is unlikely that simply increasing the iteration number
will cure the problem, but you can try: follow the standard user
response to increase the control parameter mxshak. But the
trouble is much more likely to be cured by careful consideration of
the physical system being simulated. For example, is the system
stressed in some way? Too far from equilibrium?