We have studied electronic structure, energetics, and migration of hydrogen and hydrogen complexes in GaN, based on first-principles total-energy calculations. Our calculations reveal a number of features very different from those exhibited by hydrogen in more traditional semiconductors such as Si or GaAs: a very large negative-U effect sU ø 2.4 eVd, the instability of the bond-center site, hig...

-Hydroxyl orientation has a major influence on the strength of the ionic interlayer bonding in micas because of the strong repulsion between the hydrogen and the interlayer cation (IC). In order to determine if other factors also influence the magnitude of the interlayer bond energy, the effect due to the varying H-IC distance, as one finds, for example, between a dioctahedral and a trioctahedr...

Resonance weights derived from the Natural Resonance Theory Ž . NRT , introduced in the preceding paper are used to calculate ‘‘natural bond order,’’ ‘‘natural atomic valency,’’ and other atomic and bond indices reflecting the resonance composition of the wave function. These indices are found to give Ž significantly better agreement with observed properties empirical valency, . bond lengths th...

Ionic perturbation of water has important implications in various chemical, biological and environmental processes. Previous studies revealed the structural dynamical presence ions, mainly with concentrated electrolyte solutions having significant interionic interactions. These investigations highlighted need selective extraction hydration shell from a dilute solution that is largely free Doubl...

Despite many scientific advances, human exposure to, and intoxication by, toxic metal species continues to occur. Surprisingly, little is understood about the mechanisms by which certain metals and metal-containing species gain entry into target cells. Since there do not appear to be transporters designed specifically for the entry of most toxic metal species into mammalian cells, it has been p...

The molar conductivity, Λm, of protic ionic liquids (PILs) in molecular solvents is measured at 298.15 K. The decrease in the Λm values of PILs is observed with an increase in the concentration of PILs. The limiting molar conductivities, Λm(0), were obtained for each PIL in different molecular solvents using a least squares method. The Λm(0) data for PILs were correlated with the structural asp...

Within the context of the total electron density distribution, a well-defined set of radii known as bonded radii can be derived by measuring, along the bond path, the distance between the center of an atom and the point of minimum electron density. As the properties of a crystal, including its total energy, are determined by its electron density distribution, such radii provide an objective mea...

In this work, the ability of Na(2)SO(4) and ionic liquids to induce the formation of acidic aqueous two-phase systems (ATPS) is investigated. Ternary phase diagrams, tie lines, and tie-line lengths for several systems were determined and reported at 298 K and atmospheric pressure. It is here shown that among the ionic liquids studied only those containing long alkyl side chains at the ions and/...

A study was undertaken of the solvolysis of pivaloyl triflate in a variety of ionic liquid:alcohol solvent mixtures. The solvolysis is a kΔ process (i.e., a process in which ionization occurs with rearrangement), and the resulting rearranged carbocation intermediate reacts with the alcohol cosolvent via two competing pathways: nucleophilic attack or elimination of a proton. Five different ionic...

Ionic liquids based on 1-alkyl-3-methylimidazolium cations and the hydrogen sulfate (or bisulfate) anion, HSO(4)(-), are much more viscous than ionic liquids with alkyl sulfates, RSO(4)(-). The structural origin of the high viscosity of HSO(4)(-) ionic liquids is unraveled from detailed comparison of the anion Raman bands in 1-ethyl-3-methylimidazolium hydrogen sulfate and 1-butyl-3-methylimida...