Water-cluster interactions

The SPC/E model approximates many-body effects m liquid water and corresponds to a molecular dipole moment of 2.35 Debye (D) compared to the actual dipole moment of 1.85 D for an isolated water molecule. The model reproduces the diflfiision coefficient and themiodynamics properties at ambient temperatures to within a few per cent, and the critical parameters (see below) are predicted to within 15%. The same model potential has been extended to include the interactions between ions and water by fitting the parameters to the hydration energies of small ion-water clusters. The parameters for the ion-water and water-water interactions in the SPC/E model are given in table A2.3.2. 

The ultimate reason for studying water clusters is of course to understand tire interactions in bulk water (tliough clusters are interesting in tlieir own right, too, because finite-size systems can have special properties). There has been... 

Xantheas S S 1994 Ab initio studies of cyclic water clusters (HjO), n=1-6. 2. Analysis of many-body interactions J. Chem. Phys. 100 7523-34... 

Chapman RD (2007) Organic Difluoramine Derivatives. 125 123-151 Christie RA, Jordan KD (2005) n-Body Decomposition Approach to the Calculation of Interaction Energies of Water Clusters 116 27-41... 

Caldwell J, Dang LX, Kollman PA (1990) Implementation of nonadditive intermolecular potentials by use of molecular-dynamics - development of a water water potential and water ion cluster interactions. J Am Chem Soc 112(25) 9144—9147... 

Interest in the interaction of water and nitric acid has arisen from several considerations involving such widely diverse problems as determining nitric acid uptake by water droplets and ice particles, to questions concerning the co-condensation of water and nitric acid to form polar stratospheric clouds146 and related ones about nitric acid incorporation in protonated water clusters existing in the upper atmosphere. Crutzen and Arnold suggested147 that,... 

The second necessary ingredient in the primitive quasichemical formulation is the excess chemical potential of the metal-water clusters and of water by itself. These quantities p Wm — can typically be obtained from widely available computational packages for molecular simulation [52], In hydration problems where electrostatic interactions dominate, dielectric models of those hydration free energies are usually satisfactory. The combination /t xWm — m//, wx is typically insensitive to computational approximations because the water molecules coat the surface of the awm complex, and computational errors can compensate between the bound and free ligands. 

As it is now very well known, accurate studies of the water-water interaction by means of ab-initio techniques require the use of larger and flexible basis sets and methods which consider correlation effects [85,94-96], Since high level ab-initio post-Hartree-Fock calculations are unfeasible because of their high computational cost for systems with many degrees of freedom, Density Functional Theory, more economical from the computational point of view, is being more and more considered as a viable alternative. Recently, we have presented [97] results of structural parameters and vibrational frequencies for the water clusters (H20) , n=2 to 8, using the DFT method with gradient corrected density functionals. 

Christie RA, Jordan KD (2005) -Body Decomposition Approach to the Calculation of Interaction Energies of Water Clusters 116 27-41 Clot E, Eisenstein O (2004) Agostic Interactions from a Computational Perspective One Name, Many Interpretations 113 1-36 Conley B, Atwood DA (2003) Fluoroaluminate Chemistry 104 181-193 Contreras RR, Su4rez T, Reyes M, Bellandi F, Cancines P, Moreno J, Shahgholi M, Di BUio AJ, Gray HB, Fontal B (2003) Electronic Structures and Reduction Potentials of Cu(II) Complexes of [N,N -Alkyl-bis(ethyl-2-amino-l-cyclopentenecarbothioate)] (Alkyl = Ethyl, Propyl, and Butyl) 106 71-79... 

Lee and Meisel incorporated Py, at levels of 10 M or more, into 1200 EW acid form samples that were swollen with water and with ferf-butyl alcohol. It was concluded based on the /3//1 value for water swollen samples that the Py molecules were located in the water clusters and were most likely near fluorocarbon—water interfaces. It was also concluded, based on both absorption and emission spectra, that the probes had strong interactions with the SO3 groups that were exchanged with Ag+ and Pb + cations in the case of water containing samples. Likewise, the pyrene molecules were rationalized as being surrounded by terf-butanol molecules in that case. However, excimer formation (due to the presence of adjacent pyrene molecules) in the ferf-butyl alcohol system suggested the loss of cluster morphology-... 

A theoretical study of the reaction of water and methanol with HNCO has led to a prediction of a four-centred transition state for both reactions. The interactions of water and of alcohols with alkyl isocyanates have been the subject of both experimental and theoretical study. In the case of hydration, evidence for initial interaction of water and water clusters (n = 1-3) across the N=C bond of the alkyl isocyanate... 

In the presence of traces of water, a series of ion-molecule reactions lead to the formation of proto-nated water clusters H30+(H20) . At atmospheric pressure, there is a significant interaction between reagent ions and analyte ions produced by the heated nebulizer and which will generate protonated analyte molecules [M + H]+. 

STUDY OF INTERACTION ABILITIES USING AN ENERGY PARTITIONING SCHEME IN SOME WATER CLUSTERS... 

Table 6.2 shows the detachment energy of one water molecule from a hydrated halide ion cluster [41]. The strength of the water-halide interactions is reduced as the ionic radius increases in the order of Fspecific adsorption in an electrochemical environment. It is clear that the nonspecific adsorption behavior of F is due to its strongly bound solvation shell. Due to... 

Hydrogen bonds between water molecules provide the cohesive forces that make water a liquid at room temperature and that favor the extreme ordering of molecules that is typical of crystalline water (ice). Polar biomolecules dissolve readily in water because they can replace water-water interactions with more energetically favorable water-solute interactions. In contrast, nonpolar biomolecules interfere with water-water interactions but are unable to form water-solute interactions— consequently, nonpolar molecules are poorly soluble in water. In aqueous solutions, nonpolar molecules tend to cluster together. 

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