The interaction energy is more negative in water-TMAO mixture compared to pure water. These results indicate hydrophobic solvation gets a more favorable contribution in urea-water or water-TMAO mixtures in comparison to pure water. Interestingly, it can be seen that the most favored dispersion interaction (solute-solvent) is obtained in water-urea-TMAO mixture. If we look the individual solute-solvent contribution, it is clear that E(neo-urea) is more negative than E(neo-TMAO) in different mixtures. This is because the number of urea present in the system is twice to the number of TMAO. Interestingly, it can be seen that the most favored dispersion interaction (solute-solvent) is obtained in water-urea-TMAO mixture. Contrarily, the overall association that is most in urea-TMAO solution. We already found (Table ) the unfavorable cavity formation free energy contribution in this solution is so high that overcompensate the effect of the favorable solute-solvent dispersion interaction contribution. It leads to this excessive neopentane-neopentane aggregation in urea-TMAO-water mixture relative to other three solutions. Again, the total solute-solvent energy is more negative in urea solution than that in TMAO solution still the hydrophobic association is more in aqueous urea solution that is because of this energy-entropy cancellation effect. So it is revealed that the extent of hydrophobic association in aqueous osmolyte solutions is mainly governed by the cavity formation step.