Another observation from Tables S2-S9 is that in general, the oxygen of H 2 O is a better HB acceptor as well as a better donor as compared to the sulphur of H 2 S. These observations are consistent with the general energetic rank ordering of various types of HBs in these mixed (H 2 O) m (H 2 S) n clusters, i.e., O-H…O (0.10 to 11.06 kcal mol -1 ) > O-H…S (1.36 to 6.89 kcal mol -1 ) > S-H…O (1.08 to 6.39 kcal mol -1 ) > S-H…S (1.35 to 4.23 kcal mol -