An optimisation algorithm for performing lattice energy minimisations is also implemented within the CSO-RM software library. The algorithm follows a two-stage optimisation procedure: 1) Starting from the initial vector Ω † , the intermolecular energy is locally optimised using the quasi-Newton optimisation algorithm implemented in the NAG E04UFF algorithm , and 2) following initial optimisation of the crystal structure in step 1, the estimate of Ω * is refined using a modified-Newton optimisation algorithm based on the analytical second derivatives of intermolecular energy. We find that this second stage is important when extremely high precision in the estimates of Ω * is required. This is the case when iterations are taken around the lattice minimisation, as performed in our parameter estimation methodology. Space group symmetry constraints are employed during the optimisation, and molecules in the asymmetric unit cell are assumed to be rigid.