The monomer, which lacks neighbour water molecules acting as HB acceptors or donors, falls between the two dimer cases. For the water clusters ranging in size from the trimer to the decamer, Figure shows the following order of BE strength: DDSA < DDDA < A+DDSA < A+DDDA. In these cases, all interactions involve a water acting as a double hydrogen bond donor to a different water and the organic probe, and the water accepting a single HB from a neighbouring water (DDSA) or the water accepting two HBs from two neighbouring waters (DDDA).