Water electronic structure

One of the most efficient ways to treat this problem is to combine the ab initio MO method and the RISM theory, and this has been achieved by a slight modification of the original RISM-SCF method. Effective atomic charges in liquid water are determined such that the electronic structure and the liquid properties become self-consistent, and along the route of convergence the polarization effect can be naturally incorporated. 

Carved wooden bears in all shapes and sizes overwhelmed Yngve and me at our visit to Noboribetsu in 1976. There was an afternoon to spare before the opening of the "Oji International Seminar on Theories and Ab Initio Computations of Molecular Electronic Structure" at Tomakomai, Hokkaido in the fall of 1976 so we wished to experience the hot springs. The train left us with a choice of buses, the desdnations of which were clearly indicated in Japanese writing. We found the right one and came to a city in a canyon where the sulfur fumes and hot water let themselves out. The kind reception by Kimio Ohno and Fukashi Sasaki at Hokkaido University remains a vivid memory. 

The effects of the intramicellar confinement of polar and amphiphilic species in nanoscopic domains dispersed in an apolar solvent on their physicochemical properties (electronic structure, density, dielectric constant, phase diagram, reactivity, etc.) have received considerable attention [51,52]. hi particular, the properties of water confined in reversed micelles have been widely investigated, since it simulates water hydrating enzymes or encapsulated in biological environments [13,23,53-59]. 

Huang YS, Chen YE (1988) Electronic-structure study of RuS2. Phys Rev B 38 7997-8002 Salvador P, Alonso-Vante N, Tributsch H (1998) Photoelectrocatalytic study of water oxidation at n-RuS2 electrodes. J Electrochem Soc 145 216-225... 

The different classes of Ru-based catalysts, including crystalline Chevrel-phase chalcogenides, nanostructured Ru, and Ru-Se clusters, and also Ru-N chelate compounds (RuNj), have been reviewed recently by Lee and Popov [29] in terms of the activity and selectivity toward the four-electron oxygen reduction to water. The conclusion was drawn that selenium is a critical element controlling the catalytic properties of Ru clusters as it directly modifies the electronic structure of the catalytic reaction center and increases the resistance to electrochemical oxidation of interfacial Ru atoms in acidic environments. 

In the liquid state, the molecules are still free to move in three dimensions but stiU have to be confined in a container in the same manner as the gaseous state if we expect to be able to measure them. However, there are important differences. Since the molecules in the liquid state have had energy removed from them in order to get them to condense, the translational degrees of freedom are found to be restricted. This is due to the fact that the molecules are much closer together and can interact with one another. It is this interaction that gives the Uquid state its unique properties. Thus, the molecules of a liquid are not free to flow in any of the three directions, but are bound by intermolecular forces. These forces depend upon the electronic structure of the molecule. In the case of water, which has two electrons on the ojQ gen atom which do not participate in the bonding structure, the molecule has an electronic moment, i.e.- is a "dipole". 

Correa and Waters also proposed a mechanistic scheme where the key step of the overall reaction involves the recombination of sulfonyl radicals to form an intermediate with an O—S bond, the decomposition of which yields a sulfmyl radical (ArSO") and an oxygen-centered radical ArS020 . Later this suggestion was further strengthened on the basis of ESR studies and thanks to the elucidation of the electronic structure of sulfonyl radicals. However, it seems to the author that the available literature data point to an overall mechanism for equation 17 more complex that the one suggested " (cf., for... 

PEMFC)/direct methanol fuel cell (DMFC) cathode limit the available sites for reduction of molecular oxygen. Alternatively, at the anode of a PEMFC or DMFC, the oxidation of water is necessary to produce hydroxyl or oxygen species that participate in oxidation of strongly bound carbon monoxide species. Taylor and co-workers [Taylor et ah, 2007b] have recently reported on a systematic study that examined the potential dependence of water redox reactions over a series of different metal electrode surfaces. For comparison purposes, we will start with a brief discussion of electronic structure studies of water activity with consideration of UHV model systems. 

Curioni et al.148 studied the protonation of 1,3-dioxane and 1,3,5-trioxane by means of CP molecular dynamics similations. The dynamics of both molecules was continued for few ps following protonation. The simulation provided a detailed picture the evolution of both the geometry and the electronic structure, which helped to rationalize some experimental observations. CP molecular dynamics simulations were applied by Tuckerman et al.149,150 to study the dynamics of hydronium (H30+) and hydroxyl (OH-) ions in liquid water. These ions are involved in charge transfer processes in liquid water H20 H+. .. OH2 - H20. .. H+-OH2, and HOH. . . OH- -> HO-. . . HOH. For the solvatetd H30+ ion, a picture consistent with experiment emerged from the simulation. The simulation showed that the HsO+ ion forms a complex with water molecules, the structure of which oscillates between the ones of H502 and I L/ij clusters as a result of frequent proton transfers. During a consid-... 

The final ingredient that enters the calculation is the density factor pw. This is the actual density of water appropriate to the thermodynamic state intended in the calculation. For the usual case of 1 atm. pressure and 298K, this is I gem 3. The reference density in the electronic structure calculations is p° = 1 atm//entropic cost of sequestering water in the metal-water complexes, the free energies should be adjusted by —mRT In (pi 2o/p ) = —mRTIn (1354). With these inputs the excess chemical potential is readily composed as per (9.50), provided the optimal value of m is known. This is found by composing the excess chemical potential for different assumed m values and identifying the most stable case. For the dication transition metals studied, this is found to be six, consistent with experiment [12]. 

We can expect to see future research directed at QM/MM and ab initio simulation methods to handle these electronic structure effects coupled with path integral or approximate quantum free energy methods to treat nuclear quantum effects. These topics are broadly reviewed in [32], Nuclear quantum effects for the proton in water have already received some attention [30, 76, 77]. Utilizing the various methods briefly described above (and other related approaches), free energy calculations have been performed for a wide range of problems involving proton motion [30, 67-69, 71, 72, 78-80]. 

The paper [8] includes results of investigating electron mechanisms of the impact of active particles, radicals, hydrated electrons artificially generated by plasma on the behavior of cyanide complexes of zinc in water solutions. The above investigation was conducted using quantum chemistry methods. Quantum-chemical calculation of electron structure of the complexes Zn(CN)42 4EP-20H- with complete optimization of all geometric parameters [9] was performed. 

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],... 

Rare-earth elements have been largely used in these studies. Among them, europium (III) was considered owing to its unusual electronic structure. Eu3+-ion-modified TiOz samples were prepared by a chemical coprecipitation-peptization method [156], which consists of prehydrolysis of TiCl4 by frozen distilled water. The Eu203 powder was added to the above solution to produce a transparent aqueous solution according to the required Eu3+ modifying content (Eu3+ ion equivalent to 3.0 at% of Ti in bulk solution). 

Proteins, Solid, Adsorption of Water on (Eley Leslie). Proteins and Nucleic Acids, Electronic Structure Proteins and Nucleic Acids, Influence of Physical Agents on Purine-Pyrimidine Pairs, Steroids, and Polycyclic Aromatic Carcinogens (Pullman). ... 

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