  A high level polarizable force field is used to study the temperature
dependence of hydrophobic hydration of small-sized molecules from computer
simulations. Molecular dynamics (MD) simulations of liquid water at various
temperatures form the basis of free energy perturbation calculations that
consider the onset and growth of a repulsive sphere. This repulsive sphere acts
as a model construct for the hydrophobic species. In the present study, an
extension is pursued for seven independent target temperatures, ranging from
close to the freezing point almost up to the boiling point of liquid water
under standard conditions. Care is taken to maintain proper physico-chemical
model descriptions by cross-checking with experimental water densities at the
selected target temperatures. The polarizable force field description of
molecular water turns out to be suitable throughout the entire temperature
domain considered. Derivatives of the computed free energies of hydrophobic
hydration with respect to the temperature give access to the changes in
entropy. In practice the entropy differential is determined from the negative
of the slope of tangential lines formed at a certain target temperature in the
free energy profile. The obtained changes in entropy are negative for
small-sized cavities, and hence reconfirm the basic ideas of the Lum Chandler
Weeks theory on hydrophobic hydration of small-sized solutes.
