Thanks a lot, Kohmeyer.
My full name is Zhijun Xu. 
I want to reproduce the dependence of superical critical CO2 density on the pressure.
According to the refernce (simulation method and simulated results from published paper),
I determine my box size (32×32×32 ) and the number of CO2 molecules (400) with the
density 0.89). The MD simulation is peroformed in a standard NVT ensemble. Based on these,
the pressure finally obtained should be about 300atm.
The state presented here is largely above the CO2 critical conditions and the 300atm just
is a simulated point. Classical EPM2 model is applied for the CO2 molecule.
However, My average pressure is 1013.17atm, and the pressure is jumping all over the place,
that is, from a highest value to the lowest one.
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So I want to know whether this jumping phenomena is accepted and why the phenomena occurs.
I noticed that the temperature is controlled well varying from 300 to 320 (desired at 308.15k).
And with the NPT ensemble, Does the frequency/damping constant in the nose/hoover method
for press control have a special way to determine it.
Thanks again.
with best wishes.