Table Relative energies of the one water systems in kcal mol -1 . For each system, the energy of the lowest energy system under that level of theory is subtracted from the system. a The nh1nh1 ′ water system is nonzero to the thousandths place. As seen in Table , among the one water systems, the nh1 system displayed the lowest relative energy, though the nh1nh1 ′ system is very close, with less than a 0.01 kcal mol -1 difference at the B3LYP/aug-cc-pVTZ level of theory. It can be seen that the difference in relative energies between the nh1 and nh1nh1 ′ systems is accentuated with the single point calculations at higher levels of theory, but remains within 1 kcal mol -1 .