Fix POTCAR functional handling and tests.

Author: Shyue Ping Ong

pymatgen/io/vasp/sets.py

@@ -1249,15 +1249,15 @@ def __init__(
         self,
         structure: Structure,
         xc_functional: Literal["R2SCAN", "PBE", "PBE+U"] = "PBE",
-        potcar_functional="PBE_54",
+        user_potcar_functional="PBE_54",
         prev_incar=None,
         **kwargs: Any,
     ):
         """
         Args:
             structure (Structure): Structure for static calculation.
             xc_functional ('R2SCAN'|'PBE'): Exchange-correlation functional to use. Defaults to 'PBE'.
-            potcar_functional: Choice of VASP POTCAR functional and version. Defaults to 'PBE_54'.
+            user_potcar_functional: Choice of VASP POTCAR functional and version. Defaults to 'PBE_54'.
             prev_incar (Incar|str): Incar file from previous run. Default settings of MatPESStaticSet
                 are prioritized over inputs from previous runs.
             **kwargs: Passed to DictSet.
@@ -1275,9 +1275,10 @@ def __init__(
                 f"{xc_functional} is not supported."
                 " The supported exchange-correlation functionals are PBE, PBE+U and R2SCAN."
             )
-        if potcar_functional.upper() != "PBE_54":
-            raise UserWarning(f"POTCAR version ({potcar_functional}) is inconsistent with the default of PBE_54.")
-            self.potcar.functional = potcar_functional.upper()
+        if user_potcar_functional.upper() != "PBE_54":
+            raise UserWarning(f"POTCAR version ({user_potcar_functional}) is inconsistent with the recommended PBE_54.")
+
+        self.user_potcar_functional = user_potcar_functional.upper()
 
         self.kwargs = kwargs
         self.xc_functional = xc_functional

tests/io/vasp/test_sets.py

@@ -19,7 +19,7 @@
 from pymatgen.core import SETTINGS, Lattice, Species, Structure
 from pymatgen.core.surface import SlabGenerator
 from pymatgen.core.units import FloatWithUnit
-from pymatgen.io.vasp.inputs import Incar, Kpoints, Poscar
+from pymatgen.io.vasp.inputs import Incar, Kpoints, Poscar, PotcarSingle
 from pymatgen.io.vasp.outputs import Vasprun
 from pymatgen.io.vasp.sets import (
     BadInputSetWarning,
@@ -766,6 +766,8 @@ def test_default(self):
         assert default.potcar.functional == "PBE_54"
         assert default.kpoints is None
 
+        assert str(default.potcar[0]) == str(PotcarSingle.from_symbol_and_functional("Fe_pv", "PBE_54"))
+
     def test_with_prev_incar(self):
         default_prev = MatPESStaticSet(structure=self.struct, prev_incar=self.prev_incar)
         incar = default_prev.incar
@@ -838,11 +840,12 @@ def test_functionals(self):
         functional = "LDA"
         with pytest.raises(ValueError, match=f"{functional} is not supported"):
             MatPESStaticSet(self.struct, xc_functional=functional)
-        with pytest.raises(
+        with pytest.warns(
             UserWarning,
-            match="inconsistent with the default of PBE_54",
+            match="inconsistent with the recommended PBE_54",
         ):
-            MatPESStaticSet(self.struct, potcar_functional=functional)
+            diff_potcar = MatPESStaticSet(self.struct, user_potcar_functional="PBE")
+            assert str(diff_potcar.potcar[0]) == str(PotcarSingle.from_symbol_and_functional("Fe_pv", "PBE"))
 
 
 class TestMPNonSCFSet(PymatgenTest):