make c_s_max an input to functions

pybamm/input/parameters/lithium_ion/electrolytes/LiPF6_Mohtat2020/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,Peyman MPM,from MPM code
+Initial concentration in electrolyte [mol.m-3],1000,Peyman MPM,from MPM code
 Cation transference number,0.38,Peyman MPM,
 1 + dlnf/dlnc,1,,
 Typical lithium ion diffusivity [m2.s-1],5.34E-10,Scott Moura FastDFN,

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_EC_DMC_1_1_Landesfeind2019/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,default,
+Initial concentration in electrolyte [mol.m-3],1000,default,
 Cation transference number,[function]electrolyte_transference_number_EC_DMC_1_1_Landesfeind2019,Landesfeind 2019,
 1 + dlnf/dlnc,[function]electrolyte_TDF_EC_DMC_1_1_Landesfeind2019,Landesfeind 2019,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_EC_DMC_1_1_Landesfeind2019,Landesfeind 2019," "

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_EC_EMC_3_7_Landesfeind2019/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,default,
+Initial concentration in electrolyte [mol.m-3],1000,default,
 Cation transference number,[function]electrolyte_transference_number_EC_EMC_3_7_Landesfeind2019,Landesfeind 2019,
 1 + dlnf/dlnc,[function]electrolyte_TDF_EC_EMC_3_7_Landesfeind2019,Landesfeind 2019,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_EC_EMC_3_7_Landesfeind2019,Landesfeind 2019," "

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_EMC_FEC_19_1_Landesfeind2019/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,default,
+Initial concentration in electrolyte [mol.m-3],1000,default,
 Cation transference number,[function]electrolyte_transference_number_EMC_FEC_19_1_Landesfeind2019,Landesfeind 2019,
 1 + dlnf/dlnc,[function]electrolyte_TDF_EMC_FEC_19_1_Landesfeind2019,Landesfeind 2019,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_EMC_FEC_19_1_Landesfeind2019,Landesfeind 2019," "

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_Ecker2015/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,,
+Initial concentration in electrolyte [mol.m-3],1000,,
 Cation transference number,0.26,,
 1 + dlnf/dlnc,1,,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_Ecker2015,,

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_Enertech_Ai2020/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,Ai 2020,
+Initial concentration in electrolyte [mol.m-3],1000,Ai 2020,
 Cation transference number,0.38,Ai 2020,
 1 + dlnf/dlnc,[function]dlnf_dlnc_Ai2020,,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_Ai2020,, 

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_Kim2011/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1200,,
+Initial concentration in electrolyte [mol.m-3],1200,,
 Cation transference number,0.4,Reported as a function in Kim2011 (Implement later),
 1 + dlnf/dlnc,1,,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_Kim2011,,

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_Marquis2019/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,Scott Moura FastDFN,
+Initial concentration in electrolyte [mol.m-3],1000,Scott Moura FastDFN,
 Cation transference number,0.4,Scott Moura FastDFN,
 1 + dlnf/dlnc,1,,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_Capiglia1999,, 

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_Nyman2008/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,Chen 2020,
+Initial concentration in electrolyte [mol.m-3],1000,Chen 2020,
 Cation transference number,0.2594,Chen 2020,
 1 + dlnf/dlnc,1,,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_Nyman2008,Nyman 2008, 

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_Ramadass2004/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,Ramadass,
+Initial concentration in electrolyte [mol.m-3],1000,Ramadass,
 Cation transference number,0.363,Ramadass,
 1 + dlnf/dlnc,1,,
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_Ramadass2004,, 

pybamm/input/parameters/lithium_ion/electrolytes/lipf6_Valoen2005/parameters.csv

@@ -3,6 +3,7 @@ Name [units],Value,Reference,Notes
 ,,,
 # Electrolyte properties,,,
 Typical electrolyte concentration [mol.m-3],1000,,By convention
+Initial concentration in electrolyte [mol.m-3],1000,,By convention
 Cation transference number,0.38,,Assumed to be constant
 Electrolyte diffusivity [m2.s-1],[function]electrolyte_diffusivity_Valoen2005,, 
 Electrolyte conductivity [S.m-1],[function]electrolyte_conductivity_Valoen2005,,

pybamm/input/parameters/lithium_ion/experiments/1C_charge_from_empty_Mohtat2020/parameters.csv

@@ -20,5 +20,4 @@ Upper voltage cut-off [V],4.2,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],48.8682,Peyman MPM, x0 (0.0017) * Csmax_n
 Initial concentration in positive electrode [mol.m-3],31513.0,Peyman MPM, y0 (0.8907) * Csmax_p
-Initial concentration in electrolyte [mol.m-3],1000,Peyman MPM,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_Ai2020/parameters.csv

@@ -15,5 +15,4 @@ Upper voltage cut-off [V],4.2,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],24108,Ai 2020,
 Initial concentration in positive electrode [mol.m-3],21725,Ai 2020,
-Initial concentration in electrolyte [mol.m-3],1000,Ai 2020,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_Chen2020/parameters.csv

@@ -15,5 +15,4 @@ Upper voltage cut-off [V],4.2,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],29866,Chen 2020,
 Initial concentration in positive electrode [mol.m-3],17038,Chen 2020,
-Initial concentration in electrolyte [mol.m-3],1000,Chen 2020,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_Ecker2015/parameters.csv

@@ -21,5 +21,4 @@ Upper voltage cut-off [V],4.2,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3], 26120.05,,
 Initial concentration in positive electrode [mol.m-3], 12630.8,,
-Initial concentration in electrolyte [mol.m-3],1000,,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_Kim2011/parameters.csv

@@ -21,5 +21,4 @@ Upper voltage cut-off [V],4.2,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],18081,0.63*2.84E4,
 Initial concentration in positive electrode [mol.m-3],20090,0.41*4.9E4,
-Initial concentration in electrolyte [mol.m-3],1200,,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_Marquis2019/parameters.csv

@@ -20,5 +20,4 @@ Upper voltage cut-off [V],4.1,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],19986.609595075,Scott Moura FastDFN,
 Initial concentration in positive electrode [mol.m-3],30730.7554385565,Scott Moura FastDFN,
-Initial concentration in electrolyte [mol.m-3],1000,Scott Moura FastDFN,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_ORegan2021/parameters.csv

@@ -15,5 +15,4 @@ Upper voltage cut-off [V],4.4,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],28866,Chen 2020,
 Initial concentration in positive electrode [mol.m-3],13975,Chen 2020,
-Initial concentration in electrolyte [mol.m-3],1000,Chen 2020,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_Ramadass2004/parameters.csv

@@ -19,5 +19,4 @@ Upper voltage cut-off [V],4.2,,
 # Initial conditions
 Initial concentration in negative electrode [mol.m-3],22610.7,Ramadass 2002,
 Initial concentration in positive electrode [mol.m-3],25777.5,Ramadass 2002,
-Initial concentration in electrolyte [mol.m-3],1000,Ramadass,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/1C_discharge_from_full_Xu2019/parameters.csv

@@ -14,5 +14,4 @@ Upper voltage cut-off [V],4.2,,
 ,,,
 # Initial conditions
 Initial concentration in positive electrode [mol.m-3],4631,48230*0.096 adjusted so that initial voltage is <4.2V,
-Initial concentration in electrolyte [mol.m-3],1000,,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/experiments/4C_discharge_from_full_Prada2013/parameters.csv

@@ -16,5 +16,4 @@ Upper voltage cut-off [V],4.4,,
 # Initial conditions,,,
 Initial concentration in negative electrode [mol.m-3],28831.45783,Minimized to Severson Data,
 Initial concentration in positive electrode [mol.m-3],35.3766672,Minimized to Severson Data,
-Initial concentration in electrolyte [mol.m-3],1200,Lain,
 Initial temperature [K],298.15,,

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_Ai2020/graphite_electrolyte_exchange_current_density_Dualfoil1998.py

@@ -1,7 +1,9 @@
-from pybamm import exp, constants, Parameter
+from pybamm import exp, constants
 
 
-def graphite_electrolyte_exchange_current_density_Dualfoil1998(c_e, c_s_surf, T):
+def graphite_electrolyte_exchange_current_density_Dualfoil1998(
+    c_e, c_s_surf, T, c_s_max
+):
     """
     Exchange-current density for Butler-Volmer reactions between graphite and LiPF6 in
     EC:DMC.
@@ -18,6 +20,8 @@ def graphite_electrolyte_exchange_current_density_Dualfoil1998(c_e, c_s_surf, T)
         Particle concentration [mol.m-3]
     T : :class:`pybamm.Symbol`
         Temperature [K]
+    c_s_max : :class:`pybamm.Symbol`
+        Maximum particle concentration [mol.m-3]
 
     Returns
     -------
@@ -30,8 +34,6 @@ def graphite_electrolyte_exchange_current_density_Dualfoil1998(c_e, c_s_surf, T)
     E_r = 5000  # activation energy for Temperature Dependent Reaction Constant [J/mol]
     arrhenius = exp(E_r / constants.R * (1 / 298.15 - 1 / T))
 
-    c_n_max = Parameter("Maximum concentration in negative electrode [mol.m-3]")
-
     return (
-        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_n_max - c_s_surf) ** 0.5
+        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_s_max - c_s_surf) ** 0.5
     )

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_Ai2020/graphite_entropy_Enertech_Ai2020_function.py

@@ -1,4 +1,4 @@
-def graphite_entropy_Enertech_Ai2020_function(sto):
+def graphite_entropy_Enertech_Ai2020_function(sto, c_s_max):
     """
     Lithium Cobalt Oxide (LiCO2) entropic change in open circuit potential (OCP) at
     a temperature of 298.15K as a function of the stochiometry. The fit is taken

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_Ai2020/graphite_volume_change_Ai2020.py

@@ -1,4 +1,4 @@
-def graphite_volume_change_Ai2020(sto):
+def graphite_volume_change_Ai2020(sto, c_s_max):
     """
     Graphite particle volume change as a function of stochiometry [1, 2].
 
@@ -17,6 +17,9 @@ def graphite_volume_change_Ai2020(sto):
     sto: :class:`pybamm.Symbol`
         Electrode stochiometry, dimensionless
         should be R-averaged particle concentration
+    c_s_max : :class:`pybamm.Symbol`
+        Maximum particle concentration [mol.m-3]
+
     Returns
     -------
     t_change:class:`pybamm.Symbol`

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_Chen2020/graphite_LGM50_electrolyte_exchange_current_density_Chen2020.py

@@ -1,7 +1,9 @@
-from pybamm import exp, constants, Parameter
+from pybamm import exp, constants
 
 
-def graphite_LGM50_electrolyte_exchange_current_density_Chen2020(c_e, c_s_surf, T):
+def graphite_LGM50_electrolyte_exchange_current_density_Chen2020(
+    c_e, c_s_surf, T, c_s_max
+):
     """
     Exchange-current density for Butler-Volmer reactions between graphite and LiPF6 in
     EC:DMC.
@@ -21,19 +23,18 @@ def graphite_LGM50_electrolyte_exchange_current_density_Chen2020(c_e, c_s_surf,
         Particle concentration [mol.m-3]
     T : :class:`pybamm.Symbol`
         Temperature [K]
+    c_s_max : :class:`pybamm.Symbol`
+        Maximum particle concentration [mol.m-3]
 
     Returns
     -------
     :class:`pybamm.Symbol`
         Exchange-current density [A.m-2]
     """
-
     m_ref = 6.48e-7  # (A/m2)(mol/m3)**1.5 - includes ref concentrations
     E_r = 35000
     arrhenius = exp(E_r / constants.R * (1 / 298.15 - 1 / T))
 
-    c_n_max = Parameter("Maximum concentration in negative electrode [mol.m-3]")
-
     return (
-        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_n_max - c_s_surf) ** 0.5
+        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_s_max - c_s_surf) ** 0.5
     )

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_Chen2020_plating/graphite_LGM50_electrolyte_exchange_current_density_Chen2020.py

@@ -1,7 +1,9 @@
-from pybamm import exp, constants, Parameter
+from pybamm import exp, constants
 
 
-def graphite_LGM50_electrolyte_exchange_current_density_Chen2020(c_e, c_s_surf, T):
+def graphite_LGM50_electrolyte_exchange_current_density_Chen2020(
+    c_e, c_s_surf, T, c_s_max
+):
     """
     Exchange-current density for Butler-Volmer reactions between graphite and LiPF6 in
     EC:DMC.
@@ -21,6 +23,8 @@ def graphite_LGM50_electrolyte_exchange_current_density_Chen2020(c_e, c_s_surf,
         Particle concentration [mol.m-3]
     T : :class:`pybamm.Symbol`
         Temperature [K]
+    c_s_max : :class:`pybamm.Symbol`
+        Maximum particle concentration [mol.m-3]
 
     Returns
     -------
@@ -32,8 +36,6 @@ def graphite_LGM50_electrolyte_exchange_current_density_Chen2020(c_e, c_s_surf,
     E_r = 35000
     arrhenius = exp(E_r / constants.R * (1 / 298.15 - 1 / T))
 
-    c_n_max = Parameter("Maximum concentration in negative electrode [mol.m-3]")
-
     return (
-        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_n_max - c_s_surf) ** 0.5
+        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_s_max - c_s_surf) ** 0.5
     )

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_Ecker2015/graphite_electrolyte_exchange_current_density_Ecker2015.py

@@ -1,7 +1,7 @@
-from pybamm import exp, constants, Parameter
+from pybamm import exp, constants
 
 
-def graphite_electrolyte_exchange_current_density_Ecker2015(c_e, c_s_surf, T):
+def graphite_electrolyte_exchange_current_density_Ecker2015(c_e, c_s_surf, T, c_s_max):
     """
     Exchange-current density for Butler-Volmer reactions between graphite and LiPF6 in
     EC:DMC.
@@ -26,6 +26,8 @@ def graphite_electrolyte_exchange_current_density_Ecker2015(c_e, c_s_surf, T):
         Particle concentration [mol.m-3]
     T : :class:`pybamm.Symbol`
         Temperature [K]
+    c_s_max : :class:`pybamm.Symbol`
+        Maximum particle concentration [mol.m-3]
 
     Returns
     -------
@@ -41,8 +43,6 @@ def graphite_electrolyte_exchange_current_density_Ecker2015(c_e, c_s_surf, T):
 
     arrhenius = exp(-E_r / (constants.R * T)) * exp(E_r / (constants.R * 296.15))
 
-    c_n_max = Parameter("Maximum concentration in negative electrode [mol.m-3]")
-
     return (
-        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_n_max - c_s_surf) ** 0.5
+        m_ref * arrhenius * c_e ** 0.5 * c_s_surf ** 0.5 * (c_s_max - c_s_surf) ** 0.5
     )

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_Kim2011/graphite_electrolyte_exchange_current_density_Kim2011.py

@@ -1,7 +1,7 @@
 from pybamm import exp, constants, Parameter
 
 
-def graphite_electrolyte_exchange_current_density_Kim2011(c_e, c_s_surf, T):
+def graphite_electrolyte_exchange_current_density_Kim2011(c_e, c_s_surf, T, c_s_max):
     """
     Exchange-current density for Butler-Volmer reactions between graphite and LiPF6 in
     EC:DMC
@@ -22,6 +22,8 @@ def graphite_electrolyte_exchange_current_density_Kim2011(c_e, c_s_surf, T):
         Particle concentration [mol.m-3]
     T : :class:`pybamm.Symbol`
         Temperature [K]
+    c_s_max : :class:`pybamm.Symbol`
+        Maximum particle concentration [mol.m-3]
 
     Returns
     -------
@@ -31,13 +33,12 @@ def graphite_electrolyte_exchange_current_density_Kim2011(c_e, c_s_surf, T):
 
     i0_ref = 36  # reference exchange current density at 100% SOC
     sto = 0.36  # stochiometry at 100% SOC
-    c_s_n_max = Parameter("Maximum concentration in negative electrode [mol.m-3]")
-    c_s_n_ref = sto * c_s_n_max  # reference electrode concentration
+    c_s_n_ref = sto * c_s_max  # reference electrode concentration
     c_e_ref = Parameter("Typical electrolyte concentration [mol.m-3]")
     alpha = 0.5  # charge transfer coefficient
 
     m_ref = i0_ref / (
-        c_e_ref ** alpha * (c_s_n_max - c_s_n_ref) ** alpha * c_s_n_ref ** alpha
+        c_e_ref ** alpha * (c_s_max - c_s_n_ref) ** alpha * c_s_n_ref ** alpha
     )
 
     E_r = 3e4
@@ -48,5 +49,5 @@ def graphite_electrolyte_exchange_current_density_Kim2011(c_e, c_s_surf, T):
         * arrhenius
         * c_e ** alpha
         * c_s_surf ** alpha
-        * (c_s_n_max - c_s_surf) ** alpha
+        * (c_s_max - c_s_surf) ** alpha
     )

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_ORegan2021/graphite_LGM50_electrolyte_exchange_current_density_ORegan2021.py

@@ -1,7 +1,9 @@
 from pybamm import exp, constants, Parameter
 
 
-def graphite_LGM50_electrolyte_exchange_current_density_ORegan2021(c_e, c_s_surf, T):
+def graphite_LGM50_electrolyte_exchange_current_density_ORegan2021(
+    c_e, c_s_surf, T, c_s_max
+):
     """
     Exchange-current density for Butler-Volmer reactions between graphite and LiPF6 in
     EC:DMC.
@@ -21,6 +23,8 @@ def graphite_LGM50_electrolyte_exchange_current_density_ORegan2021(c_e, c_s_surf
         Particle concentration [mol.m-3]
     T : :class:`pybamm.Symbol`
         Temperature [K]
+    c_s_max : :class:`pybamm.Symbol`
+        Maximum particle concentration [mol.m-3]
 
     Returns
     -------
@@ -33,13 +37,12 @@ def graphite_LGM50_electrolyte_exchange_current_density_ORegan2021(c_e, c_s_surf
     E_r = 4e4
     arrhenius = exp(E_r / constants.R * (1 / 298.15 - 1 / T))
 
-    c_n_max = Parameter("Maximum concentration in negative electrode [mol.m-3]")
     c_e_ref = Parameter("Typical electrolyte concentration [mol.m-3]")
 
     return (
         i_ref
         * arrhenius
         * (c_e / c_e_ref) ** (1 - alpha)
-        * (c_s_surf / c_n_max) ** alpha
-        * (1 - c_s_surf / c_n_max) ** (1 - alpha)
+        * (c_s_surf / c_s_max) ** alpha
+        * (1 - c_s_surf / c_s_max) ** (1 - alpha)
     )

pybamm/input/parameters/lithium_ion/negative_electrodes/graphite_ORegan2021/graphite_LGM50_entropic_change_ORegan2021.py

@@ -1,7 +1,7 @@
 from pybamm import exp, tanh
 
 
-def graphite_LGM50_entropic_change_ORegan2021(sto):
+def graphite_LGM50_entropic_change_ORegan2021(sto, c_s_max):
     """
     LG M50 Graphite entropic change in open circuit potential (OCP) at a temperature of
     298.15K as a function of the stochiometry. The fit is taken from [1].