AMBER Archive (2003)

Subject: AMBER: Pressure during MD

From: Joćo Barroso (joao.barroso_at_ibmb.uib.no)
Date: Sun Nov 16 2003 - 12:12:18 CST

Hello Amber users,

I'm rather new with Amber, so I have a simple question regarding the
pressure of the system during MD. I'm using Amber 7 and a periodic system
at 300 K. I'm running first equilibration at constant volume (ntb=1 and
ntp=0), and I change to constant pressure for the MD (ntb=2 and ntp=1). I
didn't give any value for "press0", assuming that it would be the default
value of 1 atm. However, in each step the output file reads press=0.0 both
in equilibration and the remaining simulation (see example below). Should I
be concerned about this? Is the system running at 1 atm or do I have to
specify the pressure in the input file?

  NSTEP =1365000 TIME(PS) = 1365.000 TEMP(K) = 299.63 PRESS = 0.0
  Etot = -63273.9308 EKtot = 26416.5302 EPtot = -89690.4610
  BOND = 15843.0623 ANGLE = 3334.9801 DIHED = 2305.3420
  1-4 NB = 1430.4541 1-4 EEL = 10987.8157 VDWAALS = 11638.1704
  EELEC = -135230.2857 EHBOND = 0.0000 RESTRAINT = 0.0000
  Ewald error estimate: 0.2029E-04
  ------------------------------------------------------------------------------

Thanks for your help

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