Water-copper interactions

The coarse-grained approach utilizes a simplified system representation with fewer degrees of freedom, resulting in faster simulations but with reduced spatial and/or temporal resolution [97-99]. Different coarse-graining (CG) schemes have been devised to preserve the most relevant properties of the molecular system. Such methods can be applied to describe time scales that are far beyond the scope of allatom M D or KMC simulations, and thus extend the scope of molecular simulation to the nanoscale. Some examples of successful application of CG methods are the simulation of the different phases of the lipid-water system, interactions of peptides and proteins with biological membranes, and the electrodeposition of copper to form nanowires, nanofilms and nanoclusters in kinetic-limited regimes [182]. 

Apart from the His-61 bridge, the two structures reveal significant differences in the coordination geometry of the copper sites in the two subunits (A and B). In the A subunit the copper geometry can be described as a fiattened tetrahedron with the water molecule interacting only weakly with it at 3.0 A. In the B subunit the Cu(I) coordination is better respresented by a trigonal bipyramid having as the basal plane His-44, His-46, and the water molecule (at 2.5 A), with His-61 and His-118 in the axial positions. 

Calculated by assuming a single water molecule interacting with Cu in the copper site with its protons equidistant from the ion. 

For the water-metal interaction, extended tests of the dependency of results on the basis set used were also performed using the CU-H2O dimer as a test case. The full electron description was used for the reference system. The results, calculated using the B3LYP method combined with different basis sets, were compared with those obtained at the standard HF and MP4 levels. Consequently, the least extended LANLIMB basis set was chosen for copper and the tests were focused on the choice of the basis set for the water molecule. Of all tests performed the B3LYP/ MB-6-31G method was found to give the best estimates for the CU-H2O system. An energy of -37.5 kJmol was obtained with this basis set for the ion-copper interaction the reference level defined by the MP4/full electron calculations is —42.3 kJmol. It should be mentioned that both results are close to the experimentally suggested estimate of the interaction of the water molecule with the copper electrode,ca -35 kJmoL. ... 

Copper interacts with numerous compounds normally found in natural waters. The amounts of the various copper compounds and complexes present in solution depend on water pH, temperature, and alkalinity and on the concentrations of bicarbonate, sulfide, and organic ligands. In animals, copper interacts with essential trace elements such as iron, zinc, molybdenum, manganese, nickel, and selenium and also with nonessential elements including silver, cadmium, mercury, and lead interactions may be either beneficial or harmful to the organism. The patterns of copper accumulation, metabolism, and toxicity from these interactions frequently differ from those produced by copper alone. Acknowledgment of these interactions is essential for understanding copper toxicokinetics. 

Such studies by Graf (1977) showed that Eu enriched in chemical sediments including the ore body, in the New Brunswick, Canada, massive sulfide deposits. This enrichment was ascribed to water-rock interaction. Bence and Taylor (1985) have shown that such Eu enrichment is characteristic of many massive sulfide deposits (fig. 31), and occurs in deposits in which copper, lead and zinc sulfides are precipitating near active black smokers at mid-ocean ridges sites. The enrichment in Eu appears to be due to reduction and mobilisation of rocks with hydrothermal fluids (Sverjensky 1984). Whitford et al. (1987) have found evidence for extensive... 

Halley and Mazzolo l develop>ed a flrst-principles-based direct dynamics method to examine the water/copper metal interface. Previous models on the electrochemical metal/ water interface published in the literature could not straightforwardly describe the asymmetry of the capacitance measured experimentally in the double layer. In approach taken by Halley and MazoUo, the electrons in the metal are modeled quantum mechanically using a jellium-type free electron model where only the s-electrons in copper are treated. Pseudopotentials are used to describe the electron interactions with water. The water solution phase is decoupled from the electronic structure and treated by molecular dynamics simulations with explicit water molecules using classical force fields. Gouy-Chapman theory is used to treat ionic screening. The electronic structure at the interface between the metal and the water is carefully matched by p>erforming electronic structure calculations on the metal substrate after each time step in the water MD simulation. The approach was used to examine the influence of applied potential on the structm-e of the metal-water... 

Also the arene-arene interactions, as encountered in Chapter 3, are partly due to hydrophobic effects, which can be ranked among enforced hydrophobic interactions. Simultaneous coordination of an aromatic oc amino acid ligand and the dienophile to the central copper(II) ion offers the possibility of a reduction of the number of water molecules involved in hydrophobic hydration, leading to a strengthening of the arene-arene interaction. Hence, hydrophobic effects can have a beneficial influence on the enantioselectivity of organic reactions. This effect is anticipated to extend well beyond the Diels-Alder reaction. 

Corrosion of industrial alloys in alkaline waters is not as common or as severe as attack associated with acidic conditions. Caustic solutions produce little corrosion on steel, stainless steel, cast iron, nickel, and nickel alloys under most cooling water conditions. Ammonia produces wastage and cracking mainly on copper and copper alloys. Most other alloys are not attacked at cooling water temperatures. This is at least in part explained by inherent alloy corrosion behavior and the interaction of specific ions on the metal surface. Further, many dissolved minerals have normal pH solubility and thus deposit at faster rates when pH increases. Precipitated minerals such as phosphates, carbonates, and silicates, for example, tend to reduce corrosion on many alloys. 

Heat exchangers that utilize copper coils are potential candidates for galvanic corrosion due to dissolved copper salts interacting with the galvanized steel shell. This problem can be avoided by nickel plating the coils. The coils then can be separated from direct contact with the vessel via insulation. Also, it is preferable to conduct the water on the tube side of heat exchangers. 

Different samples of aqueous solution containing radionuclides of Co and Eu were prepared at different copper sulphate concentrations and constant polymer concentrations (pAM) of 15 mg/1. The addition of salt to the system was done to reduce both the repulsion forces between the radionuclides and the interaction between the polymeric chains [7]. The polymer efficiency for the prepared samples was determined, results are shown in Fig. 15. It is clear that the polymer efficiency for Eu " is higher than for Co. This can be explained by the difference in the tightly bound structured water associated with different cationic species [14,107]. On this basis, we expect that Co is more hydrated than Eu. This is due to the difference in the ionic size. The hydra-... 

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