# MD: cannot run LAMMPS after installing a new version of DeePMD-kitThis typically happens when you install a new version of DeePMD-kit and copy directly the generated `USER-DEEPMD` to a LAMMPS source code folder and re-install LAMMPS.To solve this problem, it suffices to first remove `USER-DEEPMD` from LAMMPS source code by ```bashmake no-user-deepmd```and then install the new `USER-DEEPMD`.If this does not solve your problem, try to decompress the LAMMPS source tarball and install LAMMPS from scratch again, which typically should be very fast.