Effect of nanocrystallinity on lattice dynamics in Bi2Te3 based thermoelectrics

The lattice dynamics in as‐cast and nanocrystalline thermoelectric Bi₂Te₃ based p‐type and n‐type material were investigated using inelastic neutron scattering. Generalized densities of phonon states show substantial agreement between the lattice dynamics in as‐cast samples and previous studies. The lattice dynamics in the nanocrystalline materials differ significantly from its as‐cast counterparts in the acoustic phonon regime. In nanocrystalline p‐type and n‐type compounds, the average acoustic phonon group velocity was found to be reduced to 80(5)% and 95(2)% of the value in as‐cast material. It is argued that point‐defect and strain contrast scattering may play an important role for the understanding of lattice thermal conductivity in (nanocrystalline) Bi₂Te₃ based thermoelectrics beside the observed decrease of sound velocity. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

On the Reaction Mechanism of the Complete Intermolecular O2 Transfer between Mononuclear Nickel and Manganese Complexes with Macrocyclic Ligands

The recently described intermolecular O₂ transfer between the side‐on Ni‐O₂ complex [(12‐TMC)Ni‐O₂]⁺ and the manganese complex [(14‐TMC)Mn]²⁺, where 12‐TMC and 14‐TMC are 12‐ and 14‐membered macrocyclic ligands, 12‐TMC=1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane and 14‐TMC=1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane, is studied by means of DFT methods. B3LYP calculations including long‐range corrections and solvent effects are performed to elucidate the mechanism. The potential energy surfaces (PESs) compatible with different electronic states of the reactants have been analyzed. The calculations confirm a two‐step reaction, with a first rate‐determining bimolecular step and predict the exothermic character of the global process. The relative stability of the products and the reverse barrier are in line with the fact that no reverse reaction is experimentally observed. An intermediate with a μ‐η¹:η¹‐O₂ coordination and two transition states are identified on the triplet PES, slightly below the corresponding stationary points of the quintet PES, suggesting an intersystem crossing before the first transition state. The calculated activation parameters and the relative energies of the two transition sates and the products are in very good agreement with the experimental data. The calculations suggest that a superoxide anion is transferred during the reaction.     

Iodonium Metathesis Reactions

A metathesis reaction occurs when a diaryliodonium triflate is heated with an aryl iodide, resulting in the formation of a new diaryliodonium triflate.     

Self-assembled alkanethiol structures on gold: A further insight into the origins of structural rearrangement phenomena

Self-assembled structures of alkanethiols that have been deposited on gold from ethanolic solutions are susceptible to both chemical and physical changes: ethanol provides a medium for the formation of S-alkyl hydrogen thiocarbonates and related compounds via reaction with dissolved, atmospheric, CO₂. Deposition from ethanolic solutions results in multilayered structures incorporating these compounds, which at room temperature are susceptible to time-dependent structural rearrangement and molecular migration.     

Distributions with Heavy Tails in Orlicz Spaces

This paper relies on the application of Kantorovich functionals on quasi-interior points of the positive cone for certain classes of Orlicz spaces. Particularly we provide the asymptotic calculation of the ruin probability in the renewal risk model under heavy-tailed claims in the Orlicz spaces. This application assures the extension of classical asymptotic theory of regular variation.     

A Monoidal Category for Perturbed Defects in Conformal Field Theory

Starting from an abelian rigid braided monoidal category C{\mathcal{C}} we define an abelian rigid monoidal category C_F{\mathcal{C}_F} which captures some aspects of perturbed conformal defects in two-dimensional conformal field theory. Namely, for V a rational vertex operator algebra we consider the charge-conjugation CFT constructed from V (the Cardy case). Then C = Rep(V){\mathcal{C} = {\rm Rep}(V)} and an object in C_F{\mathcal{C}_F} corresponds to a conformal defect condition together with a direction of perturbation. We assign to each object in C_F{\mathcal{C}_F} an operator on the space of states of the CFT, the perturbed defect operator, and show that the assignment factors through the Grothendieck ring of C_F{\mathcal{C}_F}. This allows one to find functional relations between perturbed defect operators. Such relations are interesting because they contain information about the integrable structure of the CFT.     

A simple and effective method for phosphoryl transfer using TiCl(4) catalysis

[reaction: see text] A number of Lewis acids have been evaluated as catalysts for the phosphoryl transfer, the most efficient being TiCl(4). Application of this methodology to the phosphorylation of a number of representative target alcohols is presented     

Nonlocal dynamics of spontaneous imbibition fronts

We have studied spontaneous imbibition fronts generated by capillary rise between two roughened glass plates, the separation d of which varied between 10 and 50 microm. Perfect agreement with Washburn's law was obtained. We have determined the roughness exponent chi of the fronts, and found chi=0.81+/-0.01 for small length scales. Above a certain crossover length xi, it reached chi=0.58+/-0.04, as predicted by the quenched noise Kardar-Parisi-Zhang equation. The crossover length is found to scale with the plate separation as sqrt[d], as predicted by recent models which properly include nonlocal dynamics effects on the front. We believe this to be the first clear identification of crossover from nonlocal to local dynamics.     

Irreversibility and polymer adsorption

Physisorption or chemisorption from dilute polymer solutions often entails irreversible polymer-surface bonding. We present a theory of the resultant nonequilibrium layers. While the density profile and loop distribution are the same as for equilibrium layers, the final layer comprises a tightly bound inner part plus an outer part whose chains make only fN surface contacts where N is chain length. The contact fractions f follow a broad distribution, P(f) approximately f(-4/5), in rather close agreement with strong physisorption experiments [H. M. Schneider, Langmuir 12, 994 (1996)]].