Pressure value fluctuations

Hi all,

Just a general question. Whenever we do NPT for relaxation. Once the system relaxes the pressure fluctuates around the value we provided. Is there any acceptable value for those fluctuations? For in one case I used

fix 1 all npt temp 300 300 0.05 x 0 0 0.5 y 0 0 0.5

for a single Graphene sheet with periodic boundary conditions and metals units.


This the what I get. Though it fluctutates around 0. The pressure varies from -500 to 500.

Thank you for the help,

Deepak Behera

Pressure fluctuates. And it fluctuates more if your is not very compressible and if your system is small. Thus there is no “good” value. There have been plenty of discussions on the subject in the past, so please search the mailing list archives and the published literature to learn more.