The number of total merit function evaluations to reach convergence is approximately the same as for the point-charge model. Accurate determination of the relative computational cost of the multipole model is challenging as the longer calculation times require the use of the parallel implementation of Crys-talEstimator making direct comparison challenging. Nevertheless, the cost of the algorithm should scale almost linearly with the cost of the lattice minimisations. For the multipole models, approximately 1.85 seconds is required per lattice energy minimisation, hence one can expect about an order of magnitude increase in computation cost per Sobol' point optimisation (Table in the supporting information).