From: Jevgenij Raskatov (
Date: Thu Feb 19 2015 - 16:31:31 CST

Dear all,

I am running a high temperature simulation (1500 K, generalized Born
implicit solvent) in order to unfold a protein, and keep getting the
following message

ERROR: Constraint failure in RATTLE algorithm for atom 241!
ERROR: Constraint failure; simulation has become unstable.
ERROR: Exiting prematurely; see error messages above.

I tried raising cutoff and pairlistdiff from the default of 12 and 14 to 20
and 24, respectively, but the problem keeps recurring, although the failure
is listed for a different atom each time. I started from a solution
structure, and ramped the temperature up gradually. 500K and 1000K both
worked for 100 ns at 2 fs/step, each, but 1500K became problematic.

Any advice?


Dr. Jevgenij A. Raskatov
Assistant Professor in Chemistry and Biochemistry
Tel.: +1-831-459-2978
Department of Chemistry and Biochemistry
Physical Science Building 356
1156 High Street
Santa Cruz, CA
95064 USA