[gmx-users] Could not converge NPT constraints

[juan-manuel.castillo at mv.uni-kl.de]

Thank you,

At the end the problem was solved just increasing the time 
coupling constant of the barostat tau_p. The original 
value of 0.15 that I set at the beginning was too small, 
with 0.5 works fine.

On Tue, 09 Oct 2012 14:05:43 -0400
  Justin Lemkul <jalemkul at vt.edu> wrote:
> 
> 
> 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
> 
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