The sixteen-water case introduces a sampling procedure to handle the analyses of large numbers of proto-PCMs that are typical for large clusters (see Table ). The analyses were conducted in four stages. Because it is not practicable to conduct optimizations for all proto-PCMs generated, a selection procedure was devised. To illustrate the procedure, in the first stage of calculation, forty-six proto-PCMs were generated from one starting optimized parent PCM configuration. These proto-PCMs were sorted by signature length and members were selected at regularly spaced intervals to the desired number from the sorted list. This sampling procedure will be henceforth referred to as "sort-select". In summary, 109 proto-PCMs were analyzed and 10 did not optimize. Six distinct families were identified as illustrated by the swarmplot (Figure ). One PCM did not match with a hydrogen bonding family and further analysis was not pursued on it because of its relatively higher energy than the lowest energy hydrogen bonding family. The energy ranges of the points found falling in the different hydrogen bonding families are shown in Table . The energy decreased from the initial parent geometry by 51 kJ/mol and difference between the maximum and minimum energies is 56 kJ/mol.