improve: ase try to get virials from different sources (#660)

Author: link89

dpdata/plugins/ase.py

@@ -63,6 +63,8 @@ def from_labeled_system(self, atoms: ase.Atoms, **kwargs) -> dict:
         """Convert ase.Atoms to a LabeledSystem. Energies and forces
         are calculated by the calculator.
 
+        Note that this method will try to load virials from either virial field or converted from stress tensor.
+
         Parameters
         ----------
         atoms : ase.Atoms
@@ -94,13 +96,19 @@ def from_labeled_system(self, atoms: ase.Atoms, **kwargs) -> dict:
             "energies": np.array([energies]),
             "forces": np.array([forces]),
         }
-        try:
-            stress = atoms.get_stress(voigt=False)
-        except PropertyNotImplementedError:
-            pass
-        else:
-            virials = np.array([-atoms.get_volume() * stress])
-            info_dict["virials"] = virials
+
+        # try to get virials from different sources
+        virials = atoms.info.get("virial")
+        if virials is None:
+            try:
+                stress = atoms.get_stress(voigt=False)
+            except PropertyNotImplementedError:
+                pass
+            else:
+                virials = -atoms.get_volume() * stress
+        if virials is not None:
+            info_dict["virials"] = np.array([virials])
+
         return info_dict
 
     def from_multi_systems(
@@ -166,7 +174,6 @@ def to_labeled_system(self, data, *args, **kwargs) -> list[ase.Atoms]:
 
         structures = []
         species = [data["atom_names"][tt] for tt in data["atom_types"]]
-
         for ii in range(data["coords"].shape[0]):
             structure = Atoms(
                 symbols=species,