[gmx-users] Pressure estimation from NVT

[Sikandar Mashayak]

Hi

I am trying to determine pressure of water at given density and temperature
using SPC/E water model. To achieve this, I am doing NVT bulk simulations
and then using g_energy I get average pressure values. The question I have
is how accurate these average pressure predictions are?

e.g. I get average pressure of 185 bar for 300 K and 1 g/cm^3 water density,
but theoretical value for it is around 1 bar. What are the possible reasons
for this much deviation from theoretical value? Is there anything wrong with
my set up? I am using 2141 water molecules in 4*4*4 periodic box,
Nose-Hoover thermostat with 0.2ps time constant , MD algorithm with 1fs
time-step, LJ with 1.5 nm cut off and PME for electrostatics.

thanks
sikandar
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