Spiers Memorial Lecture: Effect of interaction specificity on the phase behaviour of patchy particles

We report a numerical study on the phase behaviour of a 'patch-anti-patch' model for particles with tetrahedrally arranged attractive spots. In particular, we compute the phase equilibria between the fluid and a low density diamond cubic (DC) crystal for different realizations of the patch-anti-patch interaction. By increasing the 'specificity' of the patches, i.e. lowering the number of corresponding attractive 'anti-patches' to a given patch, we find that the metastability gap between the DC freezing boundary and the liquid-gas critical point widens considerably. We argue that this effect of interaction specificity is relevant for the description of protein phase diagrams, as patch-anti-patch interactions can stabilise relatively open, ordered structures.