Water cluster structure

The first relaxation process, which is observed in the low-temperature region from — 100°C to +10° C is due to the reorientation of the water molecules in ice-like water cluster structures. It was shown that the hindered dynamics of the water molecules located within the pores reflects the interaction of the absorptive layer with the inner surfaces of the porous matrix [153,155]. 

When soluble ions or highly polar compounds are introduced into water solvation occurs because of associations, through electrostatic effects, between the solvent and solute species. The ordering of the solvent around the solute leads to a decrease in entropy, but this is compensated by the increased entropy from the breakdown of water cluster structure. 

Figure 1. The lowest-energy neutral water cluster structures (W2 i2 at 0 K) and four other iso-energetic isomers of neutral water hexamer.

The 5h values depend strongly on water amounts, silica type, and temperature. NMR cryoporometry shows that small water clusters (<1 nm) and nanodomains (up to 20 nm in size) are present at the interfaces of hydrated solid POA and silica/POA powders. Quantum chemical calculations of the H NMR spectra demonstrate the influence of POA/water cluster structure and dissociation of the PO-H bonds on the 6 values. 

The uncertainties quoted here are derived from the least squares algorithm. The residuals are small enough to suggest good fits but in each case the numbers were rather large and the uncertainties reflect that property. The fit of the S/L isotherm required special care to obtain convergence the methanol-water cluster structure of the composition range above 0.4 mass fraction is of interest. 

Snoek LC, Kroemer RT, Simons JP (2002) A spectroscopic and computational exploration of tryptophan-water cluster structures in the gas phase. Phys Chem Chem Phys 4 2130... 

Figure Bl.4.8. Top the lowest-energy structures of water clusters, from n = 2 -6. Bottom a sample...

Parks E K, Welller B H, Bechthold P S, Hoffman W F, NIeman G C, Pobo L G and Riley S J 1988 Chemical probes of metal cluster structure reactions of Iron clusters with hydrogen, ammonia and water J. Chem. Rhys. 88 1622... 

Bat ii Z and Miller R E 1996 Molecular clusters structure and dynamics of weakly bound systems J. Phys. Chem. 100 12 945-59 Liu K, Cruzan J D and Saykally R J 1996 Water clusters Science 271 929-33... 

Laasonen, K., Parrinello, M., Car, R., Lee, C., Vanderbilt, D., 1993, Structures of Small Water Clusters Using Gradient-Corrected Density Functional Theory , Chem. Phys. Lett., 207, 208. 

Nielsen, I. M. B., Seidl, E., Janssen, C. L., 1999, Accurate Structures and Binding Energies for Small Water Clusters The Water Trimer , J. Chem. Phys., 110, 9435. 

Besides water dimer, larger clusters of water molecules were extensively investigated by means of the DFT calculations87 111 114 127 128. Laasonen et al.113 studied the structure, the energies, and the vibrational frequencies of small water clusters (up to eight molecules)... 

Liquid water is an essential component of most terrestrial chemical processes, including those of living organisms. The cooperativity of H-bonding in water clusters is therefore of primary importance for understanding the structure and dynamics of pure water, as well as a vast spectrum of aqueous solvation phenomena in biotic and abiotic systems. In the present section we examine cooperativity effects for a... 

Martin Chaplin of South Bank University, London, has produced an extensive series of Web pages concerning water, its structure and properties. The home page is located at http //www.sbu.ac.uk/waler. The structure of water is discussed at http //www.sbu.ac. uk/water/clusters. html. 

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. 

Ludwig s (2001) review discusses water clusters and water cluster models. One of the water clusters discussed by Ludwig is the icosahedral cluster developed by Chaplin (1999). A fluctuating network of water molecules, with local icosahedral symmetry, was proposed by Chaplin (1999) it contains, when complete, 280 fully hydrogen-bonded water molecules. This structure allows explanation of a number of the anomalous properties of water, including its temperature-density and pressure-viscosity behaviors, the radial distribution pattern, the change in water properties on supercooling, and the solvation properties of ions, hydrophobic molecules, carbohydrates, and macromolecules (Chaplin, 1999, 2001, 2004). 

Among the recently published works, the one which showed that the cyclic structures of water clusters open up to form a linear structure above a certain threshold electric field value a was a systematic ab initio study on the effect of electric field on structure, energetics, and transition states of trimer, tetramer, and pentamer water clusters (both cyclic and acyclic) [36], Considering c/.v-butadiene as a model system, the strength and the direction of a static electric field has been used to examine the delocalization energy, the probabilities of some local electronic structures, the behavior of electron pairs, and the electronic fluctuations [37]. Another recent work performed by Rai et al. focused on the studies using the DFT and its time-dependent counterpart of effects of uniform static electric field on aromatic and aliphatic hydrocarbons [38],... 

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