LAMMPS, the molecular dynamics engine, doesn't have a replay function allowing one to go back and calculate properties on a trajectory, especially forces and energies. This came up in my work and I got started on writing some new LAMMPS code to accomplish this. I wanted to be able to calculate forces with a different potential on a trajectory. Anyway, I realized you can accomplish this just by using the LAMMPS looping variables. No new code necessary. It can be done by using the
read_dump command to load particular trajectory frame. A sample input script is below 