I 'm trying to modify the improper_distance file which calculates the potential energy through the distance between 4 atoms. Now I need to get these 4 atoms' original coordinates for further calculation, how can I do this? Atoms' original coordinates are stored in *.date file and has been read by the read_date command.
I have checked in compute displace/atom command which use the xorigin to calculate the displacement of atoms, and this commmand achieve this by building a new fix astore class. I think it's a bit compilcated. How can I achieve my purpose in a concise way?