I was wondering if someone could help me with this LAMMPS error “ERROR: Dump file does not contain requested snapshot (…/read_dump.cpp:119)”. It also says “Last command: read_dump ./dump.xyz 5000000 x y z format xyz”. I checked my dump file and a timestep of 5000000 is there, so why do I get this error? Is there a blatantly obvious fix to this? I am trying to keep running my simulation after it has already finished, so I have that command in with the rest of my simulation cade after my read_data command. I would also like it to keep adding to my already existing xyz dump file. If I write append at the end of the dump command, should that do the trick?
Please check the docs carefully. Matching against time step numbers is possible with atom style or custom style dump files, but not xyz format, since the latter “standard” does not contain a way reliably read the time step number. So read_dump will number the steps 1, 2, 3, 4 and so on.
I cannot easily check the docs myself right now, but I recall the situation is like outlined or similar.
You can append to an existing file by using dump_modify command: https://lammps.sandia.gov/doc/dump_modify.html
Please note that the xyz format does not include atom velocities, so it won’t be an exact continuation. The write_restart and restart commands are used for that. Moreover, read_dump for assumes that the first atom has ID 1, the second - 2 and so on (which is not always a case, especially when using more than one core), because the xyz format does not contain atom IDs.