Add a from_ase_atoms() method to Structure (#3812)

* Add a `from_ase_atoms()` to `Structure`

* pre-commit auto-fixes

* tweak doc str, add more tests, fix possibly unbound vars in test_structure.py

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Janosh Riebesell <[email protected]>

pymatgen/core/structure.py

@@ -939,6 +939,19 @@ def to_ase_atoms(self, **kwargs) -> Atoms:
 
         return AseAtomsAdaptor.get_atoms(self, **kwargs)
 
+    def from_ase_atoms(self, **kwargs) -> Structure:
+        """Convert ase.Atoms to pymatgen Structure.
+
+        Args:
+            kwargs: Passed to AseAtomsAdaptor.get_structure.
+
+        Returns:
+            Structure
+        """
+        from pymatgen.io.ase import AseAtomsAdaptor
+
+        return AseAtomsAdaptor.get_structure(self, **kwargs)
+
 
 class IStructure(SiteCollection, MSONable):
     """Basic immutable Structure object with periodicity. Essentially a sequence

tests/core/test_structure.py

@@ -36,7 +36,7 @@
     from ase.calculators.calculator import Calculator
     from ase.calculators.emt import EMT
 except ImportError:
-    ase = None
+    ase = Atoms = Calculator = EMT = None
 
 
 enum_cmd = which("enum.x") or which("multienum.x")
@@ -1848,6 +1848,13 @@ def test_to_ase_atoms(self):
         assert isinstance(atoms, Atoms)
         assert len(atoms) == len(self.struct)
         assert AseAtomsAdaptor.get_structure(atoms) == self.struct
+        assert Structure.from_ase_atoms(atoms) == self.struct
+
+        labeled_atoms = self.labeled_structure.to_ase_atoms()
+        assert Structure.from_ase_atoms(labeled_atoms) == self.labeled_structure
+
+        with pytest.raises(ValueError, match="ASE Atoms only supports ordered structures"):
+            self.disordered.to_ase_atoms()
 
     def test_struct_with_isotope(self):
         struct = Structure.from_file(f"{VASP_IN_DIR}/POSCAR_LiFePO4")