softmatter:Velocity autocorrelation function
From NSDL Materials Digital Library Wiki
The velocity autocorrrelation function, VACF or Cvv, is a autocorelation function relating to the dynamics of a system. The VACF shows how closely the velocity of a particle at a time t is correlated with the velocity at a reference time.
It is calculated as follows:
where N is the number of particles in the system, and vi(0) is the starting (reference) time.
For more information and examples refer to the calculating the diffusion coefficient page.