Sorry about that sir. I didn’t tell it at the beginning because I feel like it’s not really a LAMMPS command problem if it’s not due to that compute group/group.
So I want to calculate the interactions between two groups of atoms. One contains carbon atoms with diamond structure as the indenter, the other one is the debris generated during the indenter scratching on the SiC/graphene workpiece. (Here the position of graphene layers are very low so that it’s not considered in this case.) That is to say the debris are SiC. I set up dynamic group to the debris since the number of atoms would increase with the scratching. I don’t define any potential for the diamond indenter to treat it as a hard tool, and Tersoff potential is used for SiC, Morse potential for the interactions between SiC and the indenter. I attached the input file here so that you can look at the details about the configurations.
in.create (5.9 KB)
The issue I meet is that I tried to use “compute 6 chips group/group tool” to calculate the component force from the tool to the debris along the scratching direction, which is the positive direction of x-axis. The output is c_6. I analyze in the end I should be getting the component forces that are all positive values with the scratching distance increased since the indenter is pushing the debris along the positive direction along x-axis. However, in the results I have many negative values about that force. I also attached result figure here.
Because I did similar work before but with copper as the workpiece (EAM potential for copper and Morse potential between workpiece and the indenter).
The final result looks better, though there are still some negative values. I don’t know why there are negative values for the force and I thought it may be related to the compute group/group command. Thank you very much!