(320f) Role of Attractive Methane-Water Interactions In the Hydration of Methane

We explore the role of methane water interactions in the hydration of methane. When no spatial restrictions are placed on the solute water positional distribution, the resulting binding energy distribution is super-gaussian. These super-gaussian distributions are well described by extreme value distributions and suggest that a handful of near neighbor water molecules substantially impact the thermodynamics. Exclusion of water molecules from a well-defined neighborhood yields a gaussian distribution of binding energies, which allows us to decompose hydration as contributions due to packing, chemistry, fluctuation and mean field energetic terms. We find that in the case of hydration of methane, packing and mean field contributions dominate. This approach also gives us access to entropy of hydration of methane without invoking the commonly held view of ice like structuring of water around a non-polar solute. This novel approach transparently reveals the role of packing and chemistry in hydration of methane.