def METHOD_NAME(self):
    c_e_n = pybamm.Variable("concentration", domain=["negative electrode"])
    c_e_s = pybamm.Variable("concentration", domain=["separator"])
    c_e_p = pybamm.Variable("concentration", domain=["positive electrode"])
    self.c_e = pybamm.concatenation(c_e_n, c_e_s, c_e_p)
    self.c_s_n_surf = pybamm.surf(
        pybamm.Variable("particle conc", domain=["negative particle"])
    )
    self.c_s_p_surf = pybamm.surf(
        pybamm.Variable("particle conc", domain=["positive particle"])
    )
    self.variables = {
        "Negative electrolyte concentration [mol.m-3]": c_e_n,
        "Positive electrolyte concentration [mol.m-3]": c_e_p,
        "Negative particle surface concentration [mol.m-3]": self.c_s_n_surf,
        "Positive particle surface concentration [mol.m-3]": self.c_s_p_surf,
        "Negative electrode temperature [K]": 300,
        "Positive electrode temperature [K]": 300,
    }
    self.options = pybamm.BatteryModelOptions({"particle size": "single"})