[gmx-users] Could not converge NPT constraints

[Justin Lemkul]

On 10/9/12 11:31 AM, juan-manuel.castillo at mv.uni-kl.de wrote:
> I have not much experience with Gromacs, although I have worked for years on
> molecular simulations. I am trying to run a NPT simulation of 1000 SPCE water
> molecules at 293 K with the opls force field. I equilibrated the system first
> during 1 ns using a velocity rescale thermostat, a Berendsen barostat, and a
> leap-frog integration method. Then I run a simulation using the md-vv-avek
> integration method, a Nose-Hoover thermostat, and a MTTK barostat. I have tried
> to change different parameters of the simulation, but after some steps I always
> obtain the following error:
>
> Fatal error:
> Could not converge NPT constraints
>
> Anybody can help to explain what happens? I can provide input files if needed.

An .mdp file would be helpful.

The failure is coming from the done_iterating() function in 
src/mdlib/iteratedconstraints.c, and there are actually quite extensive comments 
in the code about what the function is doing.  Perhaps you can deduce some 
useful information from the description there.

-Justin

-- 
========================================

Justin A. Lemkul, Ph.D.
Research Scientist
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

========================================