Update LMAXMIX logic + test

materialsproject · Sep 16, 2021 · 932d9da · 932d9da
1 parent 08e289f
commit 932d9da
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Showing 2 changed files with 20 additions and 12 deletions.
diff --git a/pymatgen/io/vasp/sets.py b/pymatgen/io/vasp/sets.py
@@ -544,22 +544,27 @@ def incar(self) -> Incar:
             else:
                 incar[k] = v
         has_u = hubbard_u and sum(incar["LDAUU"]) > 0
-        if has_u:
-            # modify LMAXMIX if LSDA+U and you have d or f electrons
-            # note that if the user explicitly sets LMAXMIX in settings it will
-            # override this logic.
-            if "LMAXMIX" not in settings.keys():
-                # contains f-electrons
-                if any(el.Z > 56 for el in structure.composition):
-                    incar["LMAXMIX"] = 6
-                # contains d-electrons
-                elif any(el.Z > 20 for el in structure.composition):
-                    incar["LMAXMIX"] = 4
-        else:
+        if not has_u:
             for key in list(incar.keys()):
                 if key.startswith("LDAU"):
                     del incar[key]
 
+        # Modify LMAXMIX if you have d or f electrons present.
+        # Note that if the user explicitly sets LMAXMIX in settings it will
+        # override this logic.
+        # Previously, this was only set if Hubbard U was enabled as per the
+        # VASP manual but following an investigation it was determined that
+        # this would lead to a significant difference between SCF -> NonSCF
+        # even without Hubbard U enabled. Thanks to Andrew Rosen for
+        # investigating and reporting.
+        if "LMAXMIX" not in settings.keys():
+            # contains f-electrons
+            if any(el.Z > 56 for el in structure.composition):
+                incar["LMAXMIX"] = 6
+            # contains d-electrons
+            elif any(el.Z > 20 for el in structure.composition):
+                incar["LMAXMIX"] = 4
+
         if self.constrain_total_magmom:
             nupdown = sum([mag if abs(mag) > 0.6 else 0 for mag in incar["MAGMOM"]])
             incar["NUPDOWN"] = nupdown

diff --git a/pymatgen/io/vasp/tests/test_sets.py b/pymatgen/io/vasp/tests/test_sets.py
@@ -413,6 +413,9 @@ def test_hubbard_off_and_ediff_override(self):
         p = MPRelaxSet(self.structure, user_incar_settings={"LDAU": False, "EDIFF": 1e-10})
         self.assertNotIn("LDAUU", p.incar)
         self.assertEqual(p.incar["EDIFF"], 1e-10)
+        # after testing, we have determined LMAXMIX should still be 4 for d-block
+        # even if U is turned off (thanks Andrew Rosen for reporting)
+        self.assertEqual(p.incar["LMAXMIX"], 4)
 
     def test_write_input(self):
         self.mitset.write_input(".", make_dir_if_not_present=True)