Water molecules, belonging to the first hydration shell around a hydrophobic particle, form fewerhydrogen bonds than bulk molecules. On the other hand, the former (boundary) bonds may beslightly stronger than the latter. When two hydrophobic particles are sufficiently close to each other,the disruption of water-water hydrogen bonds in their first hydration layers can give rise to anadditional contribution to their overall interaction potential. Here we present a probabilisticapproach to studying this phenomenon. The proposed method allows one to determine the averagenumber of hydrogen bonds per water molecule in the first hydration -shell. Numerical evaluationsshow that in the interplay between a decrease in the number of boundary bonds per water moleculeand the enhancement of such a bond the former effect is clearly predominant. As a result, thedisruption of boundary hydrogen bonds, which occurs when the first two hydration shells of twoparticles overlap, leads to an attractive contribution to the overall particle interaction. Thiscontribution is naturally short range, appearing only when the separation between the two particlesbecomes smaller than four lengths of a hydrogen bond. It is greater than the overall van der Waalsinteraction potential of the same hydrophobic particles (with typical Hamaker constants) by at leastan order of magnitude.
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