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Abstract:
The hydrophobic effect of small apolar solutes is studied by molecular
dynamic (MD) simulations. Interactions between two solutes can be
described by the potential of mean force (PMF). The general feature
of the PMF between two solutes in water is a potential barrier separating
a stable contact configuration and a meta-stable solvent-separated
configuration. Interestingly, compared with classical MD simulation
results, a recent study using quantum mechanical MD simulations found
a less pronounced potential barrier and a more stable contact potential
minimum. We suggest the former is due to the use of hard-core repulsive
potentials in MD simulations, while the latter may result from different
hydrogen bond network characteristics and the strength of intermolecular
interactions between water and solutes. We examined the premise by
carrying out classical MD simulations using different functional forms
of short-range intermolecular repulsive forces. We also did a more
in-depth study of hydrogen-bond network distribution in liquid water
to characterize solvation shell structures around hydrophobic solutes.
The results elucidate the origin of differences in the PMF between
classical force-fields based MD and ab initio MD.
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Je-Luen Li
2007-07-17