To access the outlined methodology to estimate the onset of entropy, we chose the water dimer as the model system (Figure ). We calculated a set of quantum chemical descriptors along the bond dissociation, from the equilibrium to 6 Å in steps of 0.05 Å, to test their ability to detect changes in the hydrogen bond. During this process retention of the original orientation was ensured by introduction of angle constraints. Ideally, the descriptor to assess the bond breaking should be computationally inexpensive.