As can be seen from Tables and, the individual HB energies are seen to fall between 1.36 to 6.89 kcal mol - 1 . Tables S2-S5 reveal that the individual O-H…O HBs (3.62 to 11.06 kcal mol -1 ) are moderately stronger than the O-H…S HBs. The O-H…O HB energies in the dimer are also seen to be moderately stronger (3.99 to 5.69 kcal mol -1 ) than the respective O-H…S HB energies (1.84 to 4.18 kcal mol -1 ) in the dimer. The calculated values of cooperativity contribution towards the individual O-H…S HB in these clusters falls in the range between -0.83 to 3.34 kcal mol -1 . This cooperativity contribution indicates the favourable cross-association between water and hydrogen sulphides molecules in these clusters and also enhances the HB strength. As discussed earlier the negative cooperativity indicates that the HB energy in the dimers is numerically larger than the respective HB energy in the clusters. This effect is seen to be pronounced in some of these HBs. For instance, consider hydrogen bonds HB8 and HB9 in (H 2 O) 3 (H 2 S) 5 -A cluster. A closer look at these HBs (HB8 and HB9) suggests that they are involved in the formation of anti-cooperative network of HBs, where the direction of these two HBs are opposite to each other. Because of the anti-cooperative network of HBs, cooperativity contributions towards these corresponding HBs result in the smaller or negative. The cooperativity contribution towards HB8 is 0.50 kcal mol - 1 and that for HB4 is -0.21 kcal mol -1 . For this reason, the energy of these HBs is smaller (3.60 and 2.55 kcal mol - 1 , respectively). For similar reasons, the energy of HB10 in (H 2 O) 5 (H 2 S) 3 -A cluster is the smallest (1.36 kcal mol - ) among all the O-H…S HBs in these clusters. These HB energies suggest that the O-H…S HBs, in (H 2 O) m (H 2 S) n clusters are of weak to moderate strengths.