where z i is the nuclear charge. It is well-known that partial charges in non-polarisable force fields need to be scaled in some way to account for polarisation in an effective manner in condensed phase simulations. Common approaches include use of bond order corrections or charge scaling factors, but we prefer to use an implicit solvent model with a dielectric constant intermediate between the gas and water phases. The final charges thus depend on the choice of underlying QM method used to compute n(r), the choice of AIM method, and the choice of implicit solvent model and parameters. Previously we computed the electron density using the linear-scaling DFT code, ONETEP, 56 using the PBE exchange-correlation functional and a non-orthogonal generalised Wannier function basis set. A multigrid Poisson solver was used with a dielectric of 4 to pre-polarise the charges, and an implementation of the DDEC AIM method in ONETEP (similar to DDEC3 39 ) was employed to partition the electron density. As discussed in the Introduction, we now have the infrastructure in place to systematically test the effects of these hyperparameter choices. Table summarises the alternative model protocols that will be investigated here to test the effect of the underlying QM method (models 1a and 1b), the implicit solvent parameters (models 2a-2c) and AIM partitioning scheme (models 3a and 3b) on the force field parameters, and physical properties.