Dear Ahmed
I am try to simulate TIP3P water. in my simulation temperature range varies (300+/-7) K and density ~1 gr/ml that is common. but the pressure varies too much (1+/-800) bar around 1 bar. volume and kinetic energy is converged. Does pressure had capable small fluctuation around 1 bar? or it is common. I have minimized system before.
Many thanks
Yasti
Hello, Yasti:
As has been mentioned many times before, the pressure in MD simulations will fluctuate significantly, especially for small systems. Fluctuations on the order of hundreds of atmospheres are indeed possible.
If you are getting the correct pressure (in spite of the large fluctuations), the best advice I can offer is to try to run a larger system and see that the pressure is maintained while the variation in pressure decreases.
–AEI