Aqueous clusters

Luther GW, Theberge SM, Rickard DT (1999) Evidence for aqueous clusters as intermediates during zinc sulfide formation. Geochim Cosmochim Acta 64 579-579 MacKenzie KJD (1975) The calcination of titania, V. Kinetics and mechanism of the anatase-ratile transformation in the presence of additives. Trans J British Ceram Soc 74 77-87 Malek J, Mitsuhashi T, Ramirez-Castellanos J, Matsui Y (1999) Calorimetric and high-resolution transmission electron microscopy study of nanocrystallization in zirconia gel. J Mater Res 14 1834-1843... 

Theberge SM, Luther GW, Rozan TF, Rickard DT (2000) Evidence for aqueous clusters as intermediates during copper sulfide formation. Abstr Am Chem Soc 220 353 Thompson DN, Sayer RL, Noah KS (2000) Sawdust-supported passive bioremediation of western United States acid rock drainage in engineered wetland systems. Minerals Metall Process 17 96-104 Tolman RC (1966) Consideration of Gibbs theory of surface tension. J Chem Phys 16 758-774 Tolman RC (1949) The effect of droplet size on surface tension. J Chem Phys 17 333-337 Tomino H, Kusaka I, Nishioka K, Takai T (1991) Interfacial tension for small nuclei in binary nucleatioa J Crystal Growth 113 633-636... 

Aqueous clusters are sufficiently small that they can serve as experimental models for ab initio computer simulations that relate bonding to reactivity. 

Aqueous clusters have been the focus of a large number of theoretical investigations in the last few decades [30,103-113]. However, very few of these investigations have addressed their relevance in material design. 

Aqueous clusters have been widely investigated because of their ability to provide a microscopic understanding of the properties of water and their ability to yield molecular... 

One of our important contributions in the field of aqueous clusters has been to provide quantitative estimates of the effects of anharmonicity on zero point vibrational energies (ZPVE) and thermodynamic energies at finite temperatures [41]. For the water dimer, MP2/[13s8p4d2f/8s4p2d] calculations yielded values of enthalpy (AH = —3.19kcal/ mol), free energy (AG = 3.39 kcal/mol), and entropy (AS = —17.7 cal/moI/K) at 373 K, which are well within the experimental bounds (A//=—3.59 0.5 kcal/mol. 

The structures of aqueous clusters formed by the interaction of a cation, an electron, or an anion, with various sizes of water clusters bear no structural resemblance to the parent neutral water clusters because of the dominance of electrostatic interactions. However, things are very different in the case of interactions involving ir-systems with varying sizes of water clusters. This is because of the fact that the interactions existing between... 

Given the scope of this review, we desist from a detailed discussion of the energetics and vibrational spectra of the solvated aqueous clusters. However, the study of solvation phenomena can be extended to the hydration phenomena of biologically important chemical systems using Monte Carlo and molecular dynamics simulations [85-94]. More information on aqueous clusters can be obtained from our extensive work on these systems cited above. 

Unlike aqueous clusters with predominating electrostatic interaction, the interactions in metallic clusters can be classified as either continuous transitions or metallic [95,96]. In the former interaction, there is a continuous shift from one type of bonding to another type as function of a chemical or physical variable. These types of bondings include covalent, ionic, metallic, and van der Waals interactions. Thus, the accuracy of the results on metallic clusters to a large extent depends on the ability of the theoretical method to describe several types of interactions. In the case of the clusters of higher transition metals, the theoretical method should also be able to describe relativistic effects accurately. 

Initial studies on the redox properties of the M6Yi2 " clusters were reported on poorly defined complexes simply noted as [TaeCli2] or [Nb(jCli2] (122). Aqueous cluster solutions were prepared from the sulfate salts TaeCli2S04 and Nb6Cli2S04 with various electrolytes. Some combination of water molecules and anions fills the coordination sphere of the MeY " cluster. Despite these ambiguities, the oxidized compounds M6Yi2 were obtained with various chemical oxidants by a two-electron transfer process (123) ... 

Glendening, E. D. Natural energy decomposition analysis Explicit evaluation of electrostatic and polarization effects with application to aqueous clusters of alkali metal cations and neutrals. / Am. Chem. Soc., 118, 2473-2482, doi 10,1021/ja951834y (1996). 

Recently, we studied the water dependence in mixtures of water and the protonated form of Nafion [53] using both standard force field models and an empirical valence bond model to account for the Grotthuss structural diffusion mechanism of aqueous proton transport. Results showed a transition of an irregularly shaped filamentous (cylindrical) structure in the case of low water (A = 5, where A is defined as the ratio of water molecules to sulfonate groups) to a structure more in accord with the above-discussed models of nano-separation, where larger clusters form which are connected by narrow bridges. A comparison of aqueous cluster sizes indicated, for a simulation time of 30 ns, no percolating clusters for A = 5, whereas at A = 10 most water molecules were located in a connected cluster (see [53]). Other structural... 

Water is not only the product of the PEFC reaction it is also critical for stable operation. PFSA membranes require water to transport protons since they reside in aqueous clusters within the polymer and their mobility depends on the characteristics... 

P. Jungwirth and D. J. Tobias,/. Phys. Chem. A, 106(2), 379-383 (2002). Chloride Anion on Aqueous Clusters, at the Air-Water Interface, and in Liquid Water Solvent Effects on CL Polarizability. 

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