As can be seen from Table and S7, the energies of S-H…O HBs are smaller (1.08 to 6.39 kcal mol -1 ) as compared to the O-H…O (cf. Tables ) ones. However, these S-H…O HBs are of similar or little smaller strengths to those of the O-H…S (1.36 to 6.89 kcal mol -1 ) HBs. The similar strengths between these two types of HBs is also reflected from the respective HB energies in the dimers. For instance, the S-H…O HB energies in dimers fall in the range of 1.81 to 3.57 kcal mol -1 . Also, the cooperativity contribution towards these S-H…O HBs (-0.83 to 3.35 kcal mol -1 ) is similar to O-H…S (-0.83 to 3.34 kcal mol -1 ) HBs but smaller than O-H…O (-0.62 to 5.96 kcal mol -1 ) HBs. A closer look at Figures and Tables S6-S7 reveals that the energy of S-H…O HBs is a little larger when these HBs are in the immediate vicinity of stronger O-H…O and O-H…S HBs. For example, the hydrogen bonds HB1 in (H 2 O) 1 (H 2 S) 3 and HB4 in (H 2 O) 3 (H 2 S) 1 , HB5 in (H 2 O) 3 (H 2 S) 2 and HB4 in (H 2 O) 4 (H 2 S) 1 etc. have either O-H…S or O-H…O HBs as their neighbours. This observation is consistent with our earlier report; HBs become stronger if there are in the immediate vicinity of stronger neighbours.