Particle phases default option

PyBaMM Q&A Models
1

Hi,

I’ve noticed that there is a difference in simulation results when using

"particle phases": ("1", "1")

and with the default option, which, from what I understand from the source code, is just

"particle phases": "1"

Why is that, shouldn’t the two scenarios be equivalent?

MWE:

import pybamm
import matplotlib.pyplot as plt

model1 = pybamm.lithium_ion.SPMe()
model2 = pybamm.lithium_ion.SPMe(options={"particle phases": ("1", "1")})
sim1 = pybamm.Simulation(model1)
sim2 = pybamm.Simulation(model2)
sim1.solve([0, 3600])
sim2.solve([0, 3600])

fig, ax = plt.subplots(1, 1)
ax.plot(
    sim1.solution["Time [min]"].data, 
    sim1.solution["Battery voltage [V]"].data,
    label="Ub - model1"
)
ax.plot(
    sim2.solution["Time [min]"].data, 
    sim2.solution["Battery voltage [V]"].data,
    label="Ub - model2"
)
ax.set_xlabel("Time [min]")
ax.set_ylabel("Voltage [V]")
ax.legend()
plt.show()
2

That is weird, they should definitely be the same