I want to set initial velocity to a big group of atoms at the beginning of simulation.
For example I want to shoot a big block of atoms to a surface and then put pressuring it to that surface (by fix addforce).
I know that I can use “velocity set” and “velocity set (sum)” but these two will modify the velocity of group for whole simulation duration. (if I am wrong please correct me) I just want to determine initial velocity.
I also know about fix deposit, but I am not adding atoms to my simulation and I want to track the shooting group before the collision.