About applying radial velocity in fix move.

Dear lammps user,

I ma trying to move group of atom towards center of tube for a certain time step and away from the tube after that for some time step. But I couldn’t figure out the way of giving Vx Vy in fix command that will do this work. Can you please suggest me some way so that can a can apply contarction and expansion of a cylindrical tube about its vertical axis using fix move command.

in the image below I am trying to move the yellow particle radially.

You know the angular and radial position (x,y values) of each atoms. To displace atoms radially, change the x & y values accordingly. This will be easier than changing Vx & Vy.



Fix move lets you define 6 atom-style variables
which describe the x,y,z coords and x,y,z velocities
of each atom as a function of their initial position
and time. So you should be able to derive
formulas that oscillate every atom in a radial direction
and encode it in a LAMMPS variable.