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Molecular dynamics was used to compute radical and orientational distribution functions of water molecules around the different molecules: argon, methane and neopentane. It was found that the orientational distribution of water molecules on a narrow shell proximate to the neopentane molecule was very similar to that near a paraffin wall, in contrast to argon and methane.

A molecular dynamics study of the depletion of water (drying) around a single and between two hydrophobic nanoscale oblate plates in explicit water as a function of the distance of separation between them, their size, and the strength of the attraction between the plates and the water molecules is presented. A simple macroscopic thermodynamic model based on Young's law successfully predicts drying between the stacked plates and accounts for the free-energy barriers to this drying. However, because drying around a single plate is not macroscopic, a molecular theory is required to de, scribe it. The data are consistent with the ratedetermining step in the hydrophobic collapse of the two plates being a large-scale drying fluctuation, characterized by a free-energy barrier that grows with particle size. [ABSTRACT FROM AUTHOR]

In this paper we calculate the lowest 216 electronic energy surfaces of the I[sub 3] argon cluster system. We use the same approach as in our previous paper [J. Chem. Phys. 113, 6113 (2000)], but we include the presence of a solvent environment. In the absence of solvent the electronic structure of this bending triatomic molecule can be block diagonalized, and the lowest block gives rise to the lowest 64 states of the I[sub 3] molecule, further constraining the geometry of the molecule to be linear simplifies the structure of the Hamiltonian to a 3x3 matrix [J. Phys. Chem. A 103, 9552 (1999)]. We show how the solvent couples the different angular momentum states in the different manifolds allowing for transitions between otherwise forbidden diabatic angular electronic states and we predict the shape of the potentials in the cluster. We also characterize the ground state geometrical structure and properties of some of these size selected clusters. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A model for the description of the electronic ground state of the triiodide ion in solution is developed. It is based on the "diatomics in molecules" technique and is parametrized from experimental data. The solvent molecules are treated by classical intermolecular potentials. The solvent-ion interaction, which depends on the instantaneous positions of the solvent molecules, enters into the Hamiltonian matrix elements as a spatially varying external electrostatic potential. We use the model to investigate the distribution of the bond lengths of a linear triiodide ion in water at 300 K using Monte Carlo calculations. We find that under these conditions the molecule is significantly distorted with considerable redistribution of charge and bond lengths of 2.95 Å and 3.38 Å. The free energy barrier to switching bond lengths at room temperature is quite high (of the order of 10 kT) so that the distortion is predicted to have a long lifetime. The distribution of instantaneous vibrational frequencies is investigated and shows that the solvent has a greater effect on the frequency of the antisymmetric stretch than on that of the symmetric stretch vibration. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper we calculate the 64 potential energy surfaces of the manifold of states of I[sub 3] that dissociate to three ground state iodine radicals as functions of bend and stretching coordinates. We describe the set of quantum rotations necessary to generate the full Hamiltonian matrix using only I[sub 2] experimental energies and describe the formal connection between this approach and the usual diatomic in molecules Hamiltonian formulation. The I[sub 3] excited state surfaces calculated in this way are used to compute various excited state features in the photoelectron spectrum of I[sub 3][sup -] and we use these results to interpret the recently measured spectrum. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]