Dear Simen Zhou.
this problem occured to me when I wanted to apply the displacement at the radial direction. I suggest that you can modify the “displace_atom.cpp” in the lammps directory. since in the “displace_atom.cpp”, the displacement is defined as follows when flag is “move”
x[i][j]+=loads. i is the atom ID, J=0,1,2. you can modify this sentence and recompile the lammps. this will be very easy.