Allow for setting termination_ftol for film and substrate slabs separately

src/pymatgen/analysis/interfaces/coherent_interfaces.py

@@ -32,7 +32,7 @@ def __init__(
         film_miller: tuple[int, int, int],
         substrate_miller: tuple[int, int, int],
         zslgen: ZSLGenerator | None = None,
-        termination_ftol: float = 0.25,
+        termination_ftol: float | tuple[float, float] = 0.25,
         label_index: bool = False,  # necessary to add index to termination
         filter_out_sym_slabs: bool = True,
     ):
@@ -43,7 +43,8 @@ def __init__(
             film_miller (tuple[int, int, int]): miller index for the film layer
             substrate_miller (tuple[int, int, int]): miller index for the substrate layer
             zslgen (ZSLGenerator | None): BiDirectionalZSL if you want custom lattice matching tolerances for coherency.
-            termination_ftol (float): tolerance to distinguish different terminating atomic planes.
+            termination_ftol (float | tuple[float, float]): tolerances (film, substrate) to distinguish
+                different terminating atomic planes.
             label_index (bool): If True add an extra index at the beginning of the termination label.
             filter_out_sym_slabs (bool): If True filter out identical slabs with different terminations.
                 This might need to be set as False to find more non-identical terminations because slab
@@ -133,24 +134,33 @@ def _find_terminations(self):
             reorient_lattice=False,  # This is necessary to not screw up the lattice
         )
 
-        film_slabs = film_sg.get_slabs(ftol=self.termination_ftol, filter_out_sym_slabs=self.filter_out_sym_slabs)
-        sub_slabs = sub_sg.get_slabs(ftol=self.termination_ftol, filter_out_sym_slabs=self.filter_out_sym_slabs)
+        if isinstance(self.termination_ftol, tuple):
+            self.film_termination_ftol, self.substrate_termination_ftol = self.termination_ftol
+        else:
+            self.film_termination_ftol = self.substrate_termination_ftol = self.termination_ftol
+
+        film_slabs = film_sg.get_slabs(ftol=self.film_termination_ftol, filter_out_sym_slabs=self.filter_out_sym_slabs)
+        sub_slabs = sub_sg.get_slabs(
+            ftol=self.substrate_termination_ftol, filter_out_sym_slabs=self.filter_out_sym_slabs
+        )
         film_shifts = [slab.shift for slab in film_slabs]
 
         if self.label_index:
             film_terminations = [
-                label_termination(slab, self.termination_ftol, t_idx) for t_idx, slab in enumerate(film_slabs, start=1)
+                label_termination(slab, self.film_termination_ftol, t_idx)
+                for t_idx, slab in enumerate(film_slabs, start=1)
             ]
         else:
-            film_terminations = [label_termination(slab, self.termination_ftol) for slab in film_slabs]
+            film_terminations = [label_termination(slab, self.film_termination_ftol) for slab in film_slabs]
 
         sub_shifts = [slab.shift for slab in sub_slabs]
         if self.label_index:
             sub_terminations = [
-                label_termination(slab, self.termination_ftol, t_idx) for t_idx, slab in enumerate(sub_slabs, start=1)
+                label_termination(slab, self.substrate_termination_ftol, t_idx)
+                for t_idx, slab in enumerate(sub_slabs, start=1)
             ]
         else:
-            sub_terminations = [label_termination(slab, self.termination_ftol) for slab in sub_slabs]
+            sub_terminations = [label_termination(slab, self.substrate_termination_ftol) for slab in sub_slabs]
 
         self._terminations = {
             (film_label, sub_label): (film_shift, sub_shift)

tests/analysis/interfaces/test_coherent_interface.py

@@ -59,7 +59,7 @@ def setup_method(self):
     def test_termination_searching(self):
         sub_analyzer = SubstrateAnalyzer()
         matches = list(sub_analyzer.calculate(substrate=self.substrate, film=self.film))
-        cib = CoherentInterfaceBuilder(
+        cib1 = CoherentInterfaceBuilder(
             film_structure=self.film,
             substrate_structure=self.substrate,
             film_miller=matches[0].film_miller,
@@ -69,9 +69,24 @@ def test_termination_searching(self):
             label_index=True,
             filter_out_sym_slabs=False,
         )
-        assert cib.terminations == [
+        cib2 = CoherentInterfaceBuilder(
+            film_structure=self.film,
+            substrate_structure=self.substrate,
+            film_miller=matches[0].film_miller,
+            substrate_miller=matches[0].substrate_miller,
+            zslgen=sub_analyzer,
+            termination_ftol=(2, 0.1),
+            label_index=True,
+            filter_out_sym_slabs=False,
+        )
+        assert cib1.terminations == [
             ("1_Ge_P4/mmm_1", "1_Si_P4/mmm_1"),
             ("1_Ge_P4/mmm_1", "2_Si_P4/mmm_1"),
             ("2_Ge_P4/mmm_1", "1_Si_P4/mmm_1"),
             ("2_Ge_P4/mmm_1", "2_Si_P4/mmm_1"),
-        ], "termination results wrong"
+        ], "cib1 termination results wrong"
+
+        assert cib2.terminations == [
+            ("1_Ge_C2/m_2", "1_Si_P4/mmm_1"),
+            ("1_Ge_C2/m_2", "2_Si_P4/mmm_1"),
+        ], "cib2 termination results wrong"