A novel algorithm to model the influence of host lattice flexibility in molecular dynamics simulations: loading dependence of self-diffusion in carbon nanotubes

We describe a novel algorithm that includes the effect of host lattice flexibility into molecular dynamics simulations that use rigid lattices. It uses a Lowe-Andersen thermostat for interface-fluid collisions to take the most important aspects of flexibility into account. The same diffusivities and other properties of the flexible framework system are reproduced at a small fraction of the computational cost of an explicit simulation. We study the influence of flexibility on the self-diffusion of simple gases inside single walled carbon nanotubes. Results are shown for different guest molecules (methane, helium, and sulfur hexafluoride), temperatures, and types of carbon nanotubes. We show, surprisingly, that at low loadings flexibility is always relevant. Notably, it has a crucial influence on the diffusive dynamics of the guest molecules.     

The adaptable lyonsite structure

Crystal frameworks that can accommodate a wide range of elements, oxidation states, and stoichiometries are an important component of solid-state chemistry. These frameworks allow for unique comparisons of different metal-cation compositions with identical atomic arrangements. The mineral Lyonsite, alpha-Cu(3)Fe(4)(VO(4))(6), is emerging as the archetypal framework structure for a large class of materials, similar to known frameworks such as perovskite, garnet, apatite, and spinel. The new lyonsite-type oxides Li(2.82)Hf(0.795)Mo(3)O(12) and Li(3.35)Ta(0.53)Mo(3)O(12), in which hafnium and tantalum retain their highest oxidation states, are presented to advance the concept of the lyonsite structure as an adaptable framework.     

Nanoscale Chemical Imaging of the Reduction Behavior of a Single Catalyst Particle

A closer look : Investigation of the reduction properties of a single Fischer–Tropsch catalyst particle, using in situ scanning transmission X‐ray microscopy with spatial resolution of 35 nm, reveals a heterogeneous distribution of Fe⁰, Fe²⁺, and Fe³⁺ species. Regions of different reduction properties are defined and explained on the basis of local chemical interactions and catalyst morphology.

     

High-efficiency ultrasmall polarization converter in InP membrane

An ultrasmall (<10 μm length) polarization converter in InP membrane is fabricated and characterized. The device relies on the beating between the two eigenmodes of chemically etched triangular waveguides. Measurements show a very high polarization conversion efficiency of >99% with insertion losses of <-1.2 dB at a wavelength of 1.53?μm. Furthermore, our design is found to be broadband and tolerant to dimension variations.     

ChemInform Abstract: 3s-Gd2C2Br2, an Isomorph with a New Stacking Sequence

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