lmp: add unit_style requirement for compute deeptensor/atom (#2790)

The input of the model should be Angstron so that the unit style can
only be metal or real.

---------

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

source/lmp/compute_deeptensor_atom.cpp

@@ -26,6 +26,14 @@ using namespace LAMMPS_NS;
 
 ComputeDeeptensorAtom::ComputeDeeptensorAtom(LAMMPS *lmp, int narg, char **arg)
     : Compute(lmp, narg, arg), dp(lmp), tensor(nullptr) {
+  if (!(strcmp(update->unit_style, "metal") == 0 ||
+        strcmp(update->unit_style, "real") == 0)) {
+    error->all(
+        FLERR,
+        "Compute deeptensor/atom requires metal or real unit; please set it by "
+        "\"units metal\" or \"units real\"");
+  }
+
   if (narg < 4) {
     error->all(FLERR, "Illegal compute deeptensor/atom command");
   }