We present an implicit solvation approach where the interface between the quantum-mechanical solute and the surrounding environment is described by a fully continuous permittivity built up with atomic-centered "soft" spheres. This approach combines many of the advantages of the self-consistent continuum solvation model in handling solutes and surfaces in contact with complex dielectric environments or electrolytes in electronic-structure calculations. In addition it is able to describe accurately both neutral and charged systems. The continuous function, describing the variation of the permittivity, allows to compute analytically the nonelectrostatic contributions to the solvation free energy that are described in terms of the quantum surface. The whole methodology is computationally stable, provides consistent energies and forces, and keeps the computational efforts and runtimes comparable to those of standard vacuum calculations. The capabilitiy to treat arbitrary molecular or slab-like geometries as well as charged molecules is key to tackle electrolytes within mixed explicit/implicit frameworks. We show that, with given, fixed atomic radii, two parameters are sufficient to give a mean absolute error of only 1.12 kcal/mol with respect to the experimental aqueous solvation energies for a set of 274 neutral solutes. For charged systems, the same set of parameters provides solvation energies for a set of 60 anions and 52 cations with an error of 2.96 and 2.13 kcal/mol, respectively, improving upon previous literature values. To tackle elements not present in most solvation databases, a new benchmark scheme on wettability and contact angles is proposed for solid-liquid interfaces and applied to the investigation of the stable terminations of a CdS (112̅0) surface in an electrochemical medium.

The dynamics of an F-center created by an oxygen vacancy on the TiO2(110) rutile surface has been investigated using ab initio molecular dynamics. These simulations uncover a truly complex, time-dependent behavior of fluctuating electron localization topologies in the vicinity of the oxygen vacancy. Although the two excess electrons are found to populate preferentially the second subsurface layer, they occasionally visit surface sites and also the third subsurface layer. This dynamical behavior of the excess charge explains hitherto conflicting interpretations of both theoretical findings and experimental data.PACS numbers: 71.15. Pd, 73.20.At, 82.65.+r, 73.20.Jc Titanium dioxide (TiO 2 ) is one of the most thoroughly investigated metal oxides, due to its broad range of uses in several key technologies including heterogeneous catalysis, pigment materials, photocatalysis, and energy production, to name but a few [1][2][3]. It is well known that bulk and surface defects govern the properties of titania, and are thus of fundamental importance in virtually all its applications [4][5][6]. The most common point defects on the TiO 2 (110) rutile surface are oxygen vacancies (O v ) in the two-fold coordinated O rows and Ti interstitials [7,8]. In particular, removal of an O atom gives rise to two excess electrons and the appearance of new electronic states in the band gap at about 0.7-0.9 eV below the conduction band edge creating an F-center [9][10][11]. Although the two excess electrons can in principle be localized on any Ti atom, they are believed to preferentially occupy specific Ti-3d orbitals, thus formally creating Ti 3+ sites [10,12]. In stark contrast, recent experiments [13] suggest a qualitatively different viewpoint: charge localization is found to be more disperse, with the excess electrons being shared by several surface and subsurface Ti ions. Furthermore, STM/STS experiments have revealed charge delocalization involving more than ten Ti sites [14].Unfortunately, different computational methods yield conflicting results [11]. Local/semilocal density functionals (LDA/GGA) predict a rather delocalized defect level for O vacancies on TiO 2 (110) with an energy right at the bottom of the conduction band [11]. However, it is well known that such functionals bias against localization on strongly correlated d-states, and hence alternative methodologies are welcome. Recent studies of defective TiO 2 surfaces [15-21] have focused on "pragmatic and practical" correction schemes using hybrid functionals or a Hubbard correction. Although both schemes yield the expected gap states, they each predict vastly different localization topologies of the excess charge.Using B3LYP on a c(4×2) slab with an O vacancy, the defect charge is found to be localized on d -orbitals of two surface Ti atoms [15]. In particular, one unpaired electron is found on the under-coordinated Ti(11) site, while the other moves to an adjacent five-fold coordinated Ti 5c atom, such as Ti (7); see Fig. 1 for our site labeling scheme. By contrast,...

A novel metal-organic framework, [{(Zn(0.25))(8)(O)}Zn(6)(L)(12)(H(2)O)(29)(DMF)(69)(NO(3))(2)](n) (1) {H(2)L = 1,3-bis(4-carboxyphenyl)imidazolium}, has been synthesized under solvothermal conditions in good yield. It shows a Zn(8)O cluster that is coordinated to six ligands and forms an overall three-dimensional structure with channels along the crystallographic a and b axes. The imidazolium groups of the ligand moiety are aligned in the channels. The channels are not empty but are occupied by a large number of DMF and water molecules. Upon heating, these solvent molecules can be removed without breakdown of the overall structure of the framework as shown by variable-temperature powder X-ray diffraction patterns. Of great interest is the fact that the compound exhibits high proton conductivity with a low activation energy that is comparable to those of Nafion presently used in fuel cells.

Ab initio molecular dynamics simulations were performed in order to study chemisorption, electronic properties, and desorption of glycine at wet pyrite surfaces focusing on the role of surface point defects. The change in the electronic structure and its influence on the chemical reactivity of the free FeS(2)(100) surface due to sulfur vacancies was studied in detail yielding several adsorption modes of glycine and water molecules. Energetically preferred adsorption modes were furthermore investigated in the presence of hot pressurized water mimicking "Iron Sulfur World" prebiotic conditions. The metadynamics Car-Parrinello technique was employed to map the free energy landscape including paths and barriers for desorption of glycine from such wet defective surfaces. The ubiquitous sulfur vacancies are found to increase the retention time of the adsorbed amino acid by many orders of magnitudes in comparison to the ideal pyrite-water interface. The importance of these findings in terms of a possible two-dimensional primordial chemistry on mineral surfaces is discussed.

The methyl groups in TetMe-IBX lower the activation energy corresponding to the rate-determining hypervalent twisting (theoretical calculations), and the steric relay between successive methyl groups twists the structure, which manifests in significant solubility in common organic solvents. Consequently, oxidations of alcohols and sulfides occur at room temperature in common organic solvents. In situ generation of the reactive TetMe-IBX from its precursor iodo-acid, i.e., 3,4,5,6-tetramethyl-2-iodobenzoic acid, in the presence of oxone as a co-oxidant facilitates the oxidation of diverse alcohols at room temperature.