[Bug]: Cannot solve the composite SiG-anode DFN model with an initial_soc

[michelegalasso]

PyBaMM Version

23.5

Python Version

3.10.12

Describe the bug

I am trying to use the composite SiG-anode DFM model by following the guide at this link. I can reproduce the steps of the guide, but when I introduce an initial_soc value I get the following error:

KeyError: "'Negative electrode OCP [V]' not found. Use the dimensional version 'Primary: Negative electrode OCP [V]' instead."

Steps to Reproduce

import numpy as np

# load parameter values
params = pybamm.ParameterValues('Chen2020_composite')

# set current equal to C/40
params['Current function [A]'] = params['Nominal cell capacity [A.h]'] / 40

# load battery model
model = pybamm.lithium_ion.DFN({
    'particle phases': ('2', '1'),
    'open-circuit potential': (('single', 'current sigmoid'), 'single')
})

# simulate
sim = pybamm.Simulation(model, parameter_values=params)
sim.solve(t_eval=np.arange(0, 50 * 3600, 60), initial_soc=0.2)```

### Relevant log output

```shell
KeyError: "'Negative electrode OCP [V]' not found. Use the dimensional version 'Primary: Negative electrode OCP [V]' instead."

[rtimms]

Thanks for bringing this up. This is a known issue, see #2682