temperature and pressure control

From: Alessio Alexiadis (sersunzo_at_yahoo.com)
Date: Tue May 29 2007 - 00:40:02 CDT

Hello everybody,
   
  I need a piece of advice from who is more experienced than me in MD. I’m simulating water inside a (8,8) carbon nanotube and I imposed 300K and 1atm through
   
  # Constant Temperature Control
  tCouple yes
  tCoupleTemp 300
   
  # Constant Pressure Control
  BerendsenPressure yes
  BerendsenPressureTarget 1.01325 ;#[bar]
  BerendsenPressureCompressibility 0.0000457 ;#[bar-1]water
  BerendsenPressureRelaxationTime 400 ;# [fs] BerendsenPressureFreq 8
   
  The simulation run for 2 ns with timestep 2fs using PME. The nanotube is 27A long (x-direction) with a diameter=10.86 A. The periodic box of water, which wraps the nanotube has dimensions Lx=81A and Ly=Lz=24A.
  The fact is that the temperature drops to 148K (+-1K) and the pressure oscillates between approximately 100-150 bar and 1 bar.
  Can somebody understand what is wrong?
   
  Thanks
  Alessio

       
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