Ensure stress-induced diffusion is only enabled on electrodes that have particle mechanics

CHANGELOG.md

@@ -17,6 +17,7 @@
 
 ## Bug fixes
 
+- Added code to `base_battery_model` to ensure default options for stress-induced diffusion change correctly if particle mechanics is only enabled on one electrode ([#4944](https://github.com/pybamm-team/PyBaMM/pull/4944))
 - Fixed a bug with observing the outputs of 2D FEM simulations. ([#4912](https://github.com/pybamm-team/PyBaMM/pull/4912))
 - Fixed a bug in simulating FEM models with the `IDAKLUSolver`. ([#4879](https://github.com/pybamm-team/PyBaMM/pull/4879))
 - Moved concentration inside x-averaged when calculating LLI due to LAM variables ([#4858](https://github.com/pybamm-team/PyBaMM/pull/4858))

src/pybamm/models/full_battery_models/base_battery_model.py

@@ -425,6 +425,21 @@ def __init__(self, extra_options):
             and default_options["particle mechanics"] == "none"
         ):
             default_options["stress-induced diffusion"] = "false"
+        elif (
+            mechanics_option == ("none", "swelling only")
+            and default_options["particle mechanics"] == "none"
+        ):
+            default_options["stress-induced diffusion"] = ("false", "true")
+        elif (
+            mechanics_option == ("swelling only", "none")
+            and default_options["particle mechanics"] == "none"
+        ):
+            default_options["stress-induced diffusion"] = ("true", "false")
+        elif (
+            mechanics_option == ("swelling and cracking", "none")
+            and default_options["particle mechanics"] == "none"
+        ):
+            default_options["stress-induced diffusion"] = ("true", "false")
         else:
             default_options["stress-induced diffusion"] = "true"
         # The "stress-induced diffusion" option will still be overridden by

tests/unit/test_models/test_full_battery_models/test_base_battery_model.py

@@ -289,11 +289,20 @@ def test_options(self):
         assert model.options["particle mechanics"] == "swelling and cracking"
         assert model.options["stress-induced diffusion"] == "true"
 
-        # crack model
+        # particle mechanics
         with pytest.raises(pybamm.OptionError, match="particle mechanics"):
-            pybamm.BaseBatteryModel({"particle mechanics": "bad particle cracking"})
+            pybamm.BaseBatteryModel({"particle mechanics": "bad particle mechanics"})
         with pytest.raises(pybamm.OptionError, match="particle cracking"):
             pybamm.BaseBatteryModel({"particle cracking": "bad particle cracking"})
+        # check default options change correctly
+        model = pybamm.BaseBatteryModel(
+            {"particle mechanics": ("none", "swelling-only")}
+        )
+        assert model.options["stress-induced diffusion"] == ("false", "true")
+        model = pybamm.BaseBatteryModel(
+            {"particle mechanics": ("swelling-only", "none")}
+        )
+        assert model.options["stress-induced diffusion"] == ("true", "false")
 
         # SEI on cracks
         with pytest.raises(pybamm.OptionError, match="SEI on cracks"):