[AMBER] Constant temperature is not constant from the beginning

From: David Sáez <davidsaez.udec.cl>
Date: Tue, 31 Oct 2017 01:32:29 -0300

Hi, I am working on a very short QM/MM simulation and having some problems
to understand the temperature control. This is the input file I am using:

QM/MM Molecular Dynamics
  nstlim=10000, dt=0.0005, imin=0, ntpr=2000, ntwx=2000, ntwr=2000,
  tempi=300.0,temp0=300.0, ntt=1, tautp=2.0, ig=209858, irest=0, ntx=1,
  ntc=1, ntf=1, cut=8.0, ntb=1,
  qm_ewald=1, qm_pme=1

Coordinates are read from an energy minimization rst file, so I assigned
tempi=300.0 and temp0=300.0. Since the dynamics is very short, I was
expecting to have a constant temperature from the beginning.

It started at 299.40 K, but later temperatures were:

1 ps: 188.22K
2 ps: 212.79K
3 ps: 231.05K

and so on. Is this normal and I should give the simulation more time to
reach the 300K value, or am I doing something wrong?

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Received on Mon Oct 30 2017 - 22:00:03 PDT
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