Precise and accurate determination of the pKw of water via a new protocol within the Blue Moon ensemble

Water self-dissociation is one of the most studied reactions in aqueous medium, having received a special attention from the computational chemistry community. However, a precise and accurate in silico estimation of the pKw remained elusive for a long time, until very recent works finally reached this goal with a strong technical effort. In this work, I define a very accessible procedure within the Blue Moon ensemble approach that allows a precise determination of the pKw , correcting two effects present in the regular application of different constrained MD methods that caused a wrong description of the dissociated state. This approach, together with an extremely efficient ab initio setup within the Second-generation Car–Parrinello MD scheme, and a description of the electronic structure at the RPBE-D3 level, yields an estimation of the pKw that is practically equal to the experimental value of heavy water.