simplify nondimensionalisation of kinetics

CHANGELOG.md

@@ -14,6 +14,7 @@
 
 ## Optimizations
 
+-   Simplified scaling for the exchange-current density. The dimensionless parameter `C_r` is kept, but no longer used anywhere ([#2238](https://github.com/pybamm-team/PyBaMM/pull/2238))
 -   Added limits for variables in some functions to avoid division by zero, sqrt(negative number), etc ([#2213](https://github.com/pybamm-team/PyBaMM/pull/2213))
 
 # [v22.7](https://github.com/pybamm-team/PyBaMM/tree/v22.7) - 2022-07-31

pybamm/models/full_battery_models/lithium_ion/basic_dfn.py

@@ -123,7 +123,7 @@ def __init__(self, name="Doyle-Fuller-Newman model"):
         # right side. This is also accessible via `boundary_value(x, "right")`, with
         # "left" providing the boundary value of the left side
         c_s_surf_n = pybamm.surf(c_s_n)
-        j0_n = param.n.gamma * param.n.j0(c_e_n, c_s_surf_n, T) / param.n.C_r
+        j0_n = param.n.j0(c_e_n, c_s_surf_n, T)
         j_n = (
             2
             * j0_n
@@ -132,7 +132,7 @@ def __init__(self, name="Doyle-Fuller-Newman model"):
             )
         )
         c_s_surf_p = pybamm.surf(c_s_p)
-        j0_p = param.p.gamma * param.p.j0(c_e_p, c_s_surf_p, T) / param.p.C_r
+        j0_p = param.p.j0(c_e_p, c_s_surf_p, T)
         j_s = pybamm.PrimaryBroadcast(0, "separator")
         j_p = (
             2

pybamm/models/full_battery_models/lithium_ion/basic_dfn_half_cell.py

@@ -124,7 +124,7 @@ def __init__(self, options=None, name="Doyle-Fuller-Newman half cell model"):
         b_e_w = param.p.b_e
 
         # Interfacial reactions
-        j0_w = param.p.j0(c_e_w, c_s_surf_w, T) / param.p.C_r
+        j0_w = param.p.j0(c_e_w, c_s_surf_w, T)
         U_w = param.p.U
         ne_w = param.p.ne
 

pybamm/models/full_battery_models/lithium_ion/basic_spm.py

@@ -139,8 +139,8 @@ def __init__(self, name="Single Particle Model"):
         # (Some) variables
         ######################
         # Interfacial reactions
-        j0_n = param.n.gamma * param.n.j0(1, c_s_surf_n, T) / param.n.C_r
-        j0_p = param.p.gamma * param.p.j0(1, c_s_surf_p, T) / param.p.C_r
+        j0_n = param.n.j0(1, c_s_surf_n, T)
+        j0_p = param.p.j0(1, c_s_surf_p, T)
         eta_n = (2 / param.n.ne) * pybamm.arcsinh(j_n / (2 * j0_n))
         eta_p = (2 / param.p.ne) * pybamm.arcsinh(j_p / (2 * j0_p))
         phi_s_n = 0

pybamm/models/submodels/interface/base_interface.py

@@ -106,11 +106,7 @@ def _get_exchange_current_density(self, variables):
                     c_e = c_e.orphans[0]
                     T = T.orphans[0]
 
-            j0 = (
-                domain_param.gamma
-                * domain_param.j0(c_e, c_s_surf, T)
-                / domain_param.C_r
-            )
+            j0 = domain_param.j0(c_e, c_s_surf, T)
 
         elif self.reaction == "lithium metal plating":
             j0 = param.j0_plating(c_e, 1, T)

pybamm/parameters/lithium_ion_parameters.py

@@ -887,9 +887,7 @@ def j0(self, c_e, c_s_surf, T):
         c_s_surf_dim = c_s_surf * self.c_max
         T_dim = self.main_param.Delta_T * T + self.main_param.T_ref
 
-        return (
-            self.j0_dimensional(c_e_dim, c_s_surf_dim, T_dim) / self.j0_ref_dimensional
-        )
+        return self.j0_dimensional(c_e_dim, c_s_surf_dim, T_dim) / self.j_scale
 
     def U(self, c_s, T):
         """Dimensionless open-circuit potential in the electrode"""

tests/unit/test_expression_tree/test_symbol.py

@@ -34,6 +34,8 @@ def check_are_equal(children1, children2):
     def test_symbol_domains(self):
         a = pybamm.Symbol("a", domain="test")
         self.assertEqual(a.domain, ["test"])
+        # test for updating domain with same as existing domain
+        a.domains = {"primary": ["test"]}
         self.assertEqual(a.domains["primary"], ["test"])
         a = pybamm.Symbol("a", domain=["t", "e", "s"])
         self.assertEqual(a.domain, ["t", "e", "s"])

tests/unit/test_parameters/test_lithium_ion_parameters.py

@@ -66,10 +66,6 @@ def test_lithium_ion(self):
             8,
         )
 
-        np.testing.assert_almost_equal(
-            values.evaluate(param.n.gamma / param.n.C_r * c_rate), 26.6639, 3
-        )
-
         # j0_p
         np.testing.assert_almost_equal(
             values.evaluate(
@@ -79,11 +75,6 @@ def test_lithium_ion(self):
             8,
         )
 
-        # gamma_p / C_r_p
-        np.testing.assert_almost_equal(
-            values.evaluate(param.p.gamma / param.p.C_r * c_rate), 1.366, 3
-        )
-
         # particle dynamics
         # neg diffusion coefficient
         np.testing.assert_almost_equal(