RE: AMBER: molecule blowing apart during equilibration

From: Ross Walker <ross.rosswalker.co.uk>
Date: Fri, 18 Feb 2005 08:56:30 -0800

Dear Julie,

> in a lattice is blowing apart at the equilibrium stage. The
> output of the
> equilibration
> follows. Is it obvious which parameter blows up first? Can

> NSTEP = 0 TIME(PS) = 0.000 TEMP(K) =
> NSTEP = 1 TIME(PS) = 0.005 TEMP(K) =
> NSTEP = 2 TIME(PS) = 0.010 TEMP(K) =

You are taking a 5fs time step. This leads to integration errors and will
prevent you from obtaining a stable trajectory. Typically if you use shake
on hydrogens you require a time step of 2fs or shorter. Without shake you
need 1fs or shorter.

Try it with a 1fs time step (dt=0.001) and the simulation should be fine.

All the best
Ross

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|\oss Walker

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Received on Fri Feb 18 2005 - 17:53:01 PST
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