Re: About Constraint Failure

From: Kenno Vanommeslaeghe (kvanomme_at_rx.umaryland.edu)
Date: Tue Oct 15 2013 - 12:33:23 CDT

Your "very popular errors" point to equally popular system preparation
mistakes. I'm only on this mailinglist to help people with CHARMM force
field issues. I replied because you posted a message on Sunday indicating
that you were doing potentially scary things with force fields / atom
types. Consequently, even if you manage to fix your system preparation
errors, your simulation results may or may not be correct depending on
what exactly you did with your force field (which is not clear to me).

I assume you have an advisor or senior lab member who works in this field
(if not, you probably shouldn't be trying this). Ask them how to fix your
system preparation errors.

On 10/15/2013 05:57 AM, Vidhya Sankar wrote:
> Dear sir,
> Thank you for your Previous reply
> I am running the Namd Simulation After Energy Minimization It shows Very
> Popular error as follows
>
> ERROR: Constraint failure in RATTLE algorithm for atom 1242!
>
> ERROR: Constraint failure; simulation has become unstable.
>
> ERROR: Constraint failure in RATTLE algorithm for atom 1562!
>
> ERROR: Constraint failure; simulation has become unstable.
>
> ERROR: Constraint failure in RATTLE algorithm for atom 265!
>
> ERROR: Constraint failure; simulation has become unstable.
>
> ERROR: Exiting prematurely; see error messages above.
>
> Then I using VMD To get Namd plot (for total Energy)
> It Shows the energy Suddenly falls to 7.5e+08 after 150 steps and
> Suddenly hikes to 1.60e+09 at the end Em (1000steps)
>
> How to Solve it ? Which Parameter Should I Adjust ?
>
> Should I Diagnosis The Particular atom ? then i How to Diagnosis?

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