Agreement is also excellent with DMC calculations of D 0 for the dimer using the HBB2 and MB-pol 41 potentials, both of which potentials predict 1101 cm -1 . These values are also in excellent agreement with D 0 reported for the dimer 42 using the recent flexible CCpol-8sf potential. For the water trimer the present results are in excellent agreement with previous DMC calculations using WHBB, 2724 cm -1 , and MB-pol, 2693 cm -1 . Also there is very good agreement for dissociation to three monomers, namely 3854 cm -1 for WHBB and 3794 cm -1 for MB-pol.