Reg: Pressure Fluctuations in NPT

Dear All,

I am trying to simulate a box of water having density 1gm/cm3 and 10,000 molecules using LAMMPS. The issue which I am facing is that I am not able to maintain the pressure constant. It keeps on fluctuating in the range of ±500 atm.

But still I plotted the mean square displacement(msd) and radial distribution function (rdf). The self diffusion coefficient which I calculated from msd was almost equal (1 % error) to the actual value in journal papers obtained for that water model.

Also the rdf plot exactly matched the plot given in journal papers.

So, can I conclude that pressure fluctuations of such amplitude can be ignored and I should proceed further in MD?

Pressures fluctuate, often a lot for solids and liquids.

If the time average is stable, you’re probably fine.