Overall, the use of analytical relations for evaluating the derivatives of the merit function should significantly reduce the computational cost of optimising the total merit function, while also improving the precision with which parameter estimates can be obtained. The main barrier against implementation of this approach is that many quantities necessary for the calculation, such as the Hessian matrix or the derivatives of intermolecular energy with respect to the parameter values in Equation ( ), cannot be easily obtained or implemented in any existing software for lattice minimisations. Even when such quantities could be feasibly obtained, the quantities may only be calculated approximately using finite differences. To reap the benefits that these calculations may bring necessitates the development of new tools for performing intermolecular energy calculations and lattice minimisations.