[gmx-users] Is diffusion coefficient dependent on box size?

[Pallavi Banerjee]

Hello Users,

On simulating SPC-E water, I see that I get two different values of
diffusion coefficient from two different box sizes. I get D=2.4 from a
cubic box of 3 nm and D=2.7 from a cubic box of 7 nm. All the .mdp
parameters are the same for both. The diffusion coefficients are obtained
from g_msd Any idea what could be going wrong here?

Thanks in advance!

-Pallavi Banerjee