Is it possible to update the atoms in a group during a simulation?

Dear all,

I am running a large simulation, where I want to keep track of certain particles entering a particular region. The region is cubic, so that I can pick the molecules using a simple check on x, y & z coordinates.

I want to have the velocity, and angular velocities of those particles that are within the region. If I print the velocity and angular velocities of all the particles, the file size would be extremely big. Hence, I want to selectively print those particles that are within the region in that timestep.

I tried using variable, created a group using variable, and dumped the group:

variable findCavityAtoms atom “x > xlo && x < xhi”
group cavity variable findCavityAtoms
dump 1 cavity custom 1000 x y z vx vy vz

But the group is not updated every step.

Is it possible to do it? If so, could anybody point me in the right direction?

Thanking you,

Saikat Banerjee

Groups are fixed for the duration of a simulation.

You can, however, achieve what you want by defining a region which covers your volume of interest, then passing it to dump_modify region (


Thanks. It was a great help.