Accretion disc origin of the Earth's water.

Earth's water is conventionally believed to be delivered by comets or wet asteroids after the Earth formed. However, their elemental and isotopic properties are inconsistent with those of the Earth. It was thus proposed that water was introduced by adsorption onto grains in the accretion disc prior to planetary growth, with bonding energies so high as to be stable under high-temperature conditions.

A first-principles characterization of water adsorption on forsterite grains.

Numerical simulations examining chemical interactions of water molecules with forsterite grains have demonstrated the efficacy of nebular gas adsorption as a viable mechanism for water delivery to the terrestrial planets. Nevertheless, a comprehensive picture detailing the water-adsorption mechanisms on forsterite is not yet available. Towards this end, using accurate first-principles density functional theory, we examine the adsorption mechanisms of water on the (001), (100), (010) and (110) surfaces of forsterite.

Relationship between dye-iodine binding and cell voltage in dye-sensitized solar cells: a quantum-mechanical look.

It has been proposed that iodine binding to dyes may actually decrease the cell efficiency of a dye-sensitized solar cell. A previous experimental study showed that a two-atom change from oxygen to sulfur increased recombination of iodine with injected electrons by a factor of approximately 2. Here, it is shown that iodine binding is a plausible explanation for this effect.

Adsorption of uranyl species onto the rutile (110) surface: a periodic DFT study.

To model the structures of dissolved uranium contaminants adsorbed on mineral surfaces and further understand their interaction with geological surfaces in nature, we have performed periodic density funtional theory (DFT) calculations on the sorption of uranyl species onto the TiO(2) rutile (110) surface. Two kinds of surfaces, an ideal dry surface and a partially hydrated surface, were considered in this study. The uranyl dication was simulated as penta- or hexa-coordinated in the equatorial plane.

Interactions of the N3 dye with the iodide redox shuttle: quantum chemical mechanistic studies of the dye regeneration in the dye-sensitized solar cell.

The iodide/triiodide redox couple plays a unique role in the dye-sensitized solar cell (DSSC). It is a necessary and unique part of every highly efficient DSSC published to date; alternative redox couples do not perform nearly as well. Hence, a detailed molecular-level understanding of its function is desirable.

Chalcogenophilicity of mercury.

Density-functional theory (DFT) calculations have been carried out to investigate the chalcogenophilicity of mercury (Hg) reported recently [J. Am. Chem.

Degradation mechanism of methyl mercury selenoamino acid complexes: a computational study.

Density functional theory (DFT) calculations have been carried out on the possible degradation/demethylation mechanism of methyl mercury (CH(3)Hg(+)) complexes with free cysteine and seleonocysteine. The binding of CH(3)Hg(+) ions with one (seleno)amino acid is thermodynamically favorable. However, the binding with another acid molecule is a highly unfavorable process.

Computational studies on the interactions among redox couples, additives and TiO2: implications for dye-sensitized solar cells.

One of the major and unique components of dye-sensitized solar cells (DSSC) is the iodide/triiodide redox couple. Periodic density-functional calculations have been carried out to study the interactions among three different components of the DSSC, i.e.

Synthesis, characterization and structures of methylmercury complexes with selenoamino acids.

Four new methylmercury-selenoamino acid complexes were synthesized, including methylmercury-L-selenoglutathionate, methylmercury-D,L-selenopenicillaminate, and two methylmercury-L-selenomethioninate complexes (one via a Hg-Se bonding and the other Hg-N bonding). All the complexes were characterized by NMR ((1)H, (13)C, (77)Se and (199)Hg), FT-IR and mass spectra. Their molecular structures were established by single crystal X-ray crystallography (for the Hg-N bonding methylmercury-L-selenomethioninate) and by quantum mechanical calculations using Gaussian-03 with the hybrid functional B3LYP/SDD.

Computational studies of structural, electronic, spectroscopic, and thermodynamic properties of methylmercury-amino acid complexes and their Se analogues.

Quantum chemical calculations have been carried out to study the structural, electronic, spectroscopic, and thermodynamic properties of five methylmercury-amino acid complexes and their selenium analogues. The structural properties of methylmercury-amino acids are very similar to their Se analogues except for those properties that are directly related to the Se atom which has a larger covalent radius. Characteristic stretching frequencies are observed for Hg-S/Se and Hg-C bonds.

Properties of polythiophene and related conjugated polymers: a density-functional study.

Using a parameter-free, density-functional method that has been developed explicitly for the theoretical treatment of infinite, periodic, isolated, helical polymers we study various polymers related to polythiophene. In particular we discuss how the electronic properties of polythiophene are changed when replacing some of the H atoms by CH3 group, by incorporating vinylene bridges into the backbone, or when replacing some or all the CH units of the backbone by N atoms. We observe the weakest effects for the methyl-substitution and the strongest for the N-incorporation.