[gmx-users] Diffusion constant

[pari lotfi]

Dear all,

what is the meaning of this statement?

"The diffusion constant is calculated by least squares fitting a straight
line (D*t + c) through the MSD(t) from -beginfit to -endfit (note that t is
a time from the reference positions, not simulation time)."

I calculated diffusion constant of the water in a simulation by Gromacs 4.5
and I write a c++ code for calculation of diffusion constant. Unfortunately
diffusion constant of c++ code and "g_msd" not equal.

I think the meaning of above statement helps me.

Thanks in advance,
Pari