Error with velocity


I’m trying to extract velocity around each atom in my crystal with ppp boundary condition. But when I print the velocity of the neighbors (v=atom->v, then get v[j][0], v[j][1], v[j][2] for each j in the neighbor list of i). I got zero for some atoms, which does not make sense to me. I’m guessing they are near-boundary atoms which have neighbors wrapped due to the periodic boundary condition. PS: The positions are all making sense.

Hope my description is clear. Appreciate any guidance in extracting such information correctly!


Please see the comm_modify vel command. Unless you request that velocities of ghost atoms are updated, there is no velocity data for atoms with index j >= atom->natoms. This is not done by default to reduce communication overhead.