their CHELPG charges determined as outlined above. Approach 2: infinite crystalline electrostatic potential via conductor screening. In this method, we build an approximate sphere of unit cells with an approximate radius of ~40 Å, chosen by convergence testing (Figure ), with the unit cell redefined by translation to position a single molecule of 1 in the centre of the spherical supercell. All remaining atoms in the spherical supercell are assigned their CHELPG charges (outlined above), and the entire array is embedded in a perfect conductor reaction field cavity with a radius of 40 Å using the Kirkwood solvent model with 𝜀 = ∞. The displacement vectors for phonons corresponding to arbitrary q1×q2×q3 grids can then be mapped onto the spherical supercell as required.