As an example for the power of this collaborative approach, we suggested to the authors of the best submissions to compute the results for the OH donor vibration in the water dimer, which has been a rather controversial observable over the last few years. A well-converged full-dimensional variational treatment of the donor OH stretch band origin on a high quality analytical potential energy hypersurface is now available 64 yielding a value of 3599 cm -1 . This calculation matches the experimental consensus of about 3601 cm -1 well within the ≈10 cm -1 spread due to quantum tunneling of indistinguishable Fig. Top: RMSD values (in cm -1 ) for the four submissions with the lowest RMSD overall (PH5, AC2, LS3 and LS4). Note that the ordinate axis has a much smaller range than in the previous plots, with all four sets of values remaining below an RMSD of 15 cm -1 .