[gmx-users] position and velocity in traj file & Verlet algorithm in GROMACS 3.3

[Jianwei Wang]

Two questions:

(1) What are the positions and velocities stored in trajectory files by
gmx3.3? I know the positions must be at current time (at time t), but how
about velocities? are they at t-0.5*dt, t+0.5*dt or estimated at time t? If
gmx3.3 uses leap-frog form of verlet, velocites at time t are not available
or have to be estimated. 

(2) Is the velocity verlet available? If gmx3.3 implements it, how to turn
on velocity version of Verlet? Thanks a lot!