As mentioned before, symmetry is not explicitly taken into consideration and is not enforced, aside the rotranslational relation provided by Equation (1). We assume that the environment sufficiently represents any symmetry present in the input structure. An initial cubic structure, for example, is not required to have identical stress components for the equivalent cartesian directions and does not necessarily retain three identical cell lengths. Geometry optimisation may therefore result in cell parameters that do not represent the original symmetry. Although a restriction of symmetry equivalence is possible, we chose to use unrestricted optimisations of cell parameters. This provides additional information on the performance of our method. However, it leads to some minor deviations from the symmetry in the crystal geometry due to two major factors: the background charges and some numerical noise. The problem with background charges could be resolved by using an embedding method which would place the charges in a symmetric fashion around the origin of the cluster. This is, however, far from being a limiting factor in accuracy, as one will later observe.