AMBER: Etot has downward drift in 'NVE' ensemble

From: John S. Zintsmaster <>
Date: Wed, 12 Jul 2006 22:01:08 -0400

Hello All,

I am attempting to run a microcanonical ensemble of about 6000 atoms. Here is my
input file:

  nstlim=500000, dt=0.001, ntx=5, irest=1,
  ntpr=500, ntwr=500, ntwx=500, ntwv=500,ntwe=100

  tempi=300.0, ntt=0, tautp=2.0,

  ntb=1, ntp=0,

  ntc=2, ntf=2,


I am experiencing a DOWN-ward drift in my total energy. I know that with a
similarly equilibrated system, with the same input file except for dt=0.002 I
experience the "normal" less than optimal upward drift in Etot. Has anyone had
anything like this downward drift happen to them or know of the right paramter
to tweek until a more true NVE ensemble is held. Thanks in advance.


John S. Zintsmaster
251 Nieuwland Science Hall
Dept of Chemistry and Biochemistry
University of Notre Dame
Notre Dame, IN 46556
phone:  574-631-0285
fax:  574-631-6652
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Received on Thu Jul 13 2006 - 16:34:52 PDT
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