There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Objective comparisons of electrocatalyst activity and stability using standard methods under identical conditions are necessary to evaluate the viability of existing electrocatalysts for integration into solar-fuel devices as well as to help inform the development of new catalytic systems. Herein, we use a standard protocol as a primary screen for evaluating the activity, short-term (2 h) stability, and electrochemically active surface area (ECSA) of 18 electrocatalysts for the hydrogen evolution reaction (HER) and 26 electrocatalysts for the oxygen evolution reaction (OER) under conditions relevant to an integrated solar water-splitting device in aqueous acidic or alkaline solution. Our primary figure of merit is the overpotential necessary to achieve a magnitude current density of 10 mA cm–2 per geometric area, the approximate current density expected for a 10% efficient solar-to-fuels conversion device under 1 sun illumination. The specific activity per ECSA of each material is also reported. Among HER...

Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

Bismuth vanadate (BiVO4) has a band structure that is well-suited for potential use as a photoanode in solar water splitting, but it suffers from poor electron-hole separation. Here, we demonstrate that a nanoporous morphology (specific surface area of 31.8 square meters per gram) effectively suppresses bulk carrier recombination without additional doping, manifesting an electron-hole separation yield of 0.90 at 1.23 volts (V) versus the reversible hydrogen electrode (RHE). We enhanced the propensity for surface-reaching holes to instigate water-splitting chemistry by serially applying two different oxygen evolution catalyst (OEC) layers, FeOOH and NiOOH, which reduces interface recombination at the BiVO4/OEC junction while creating a more favorable Helmholtz layer potential drop at the OEC/electrolyte junction. The resulting BiVO4/FeOOH/NiOOH photoanode achieves a photocurrent density of 2.73 milliamps per square centimenter at a potential as low as 0.6 V versus RHE.

https://science.sciencemag.org/content/sci/early/2014/02/12/science.1246913.full.pdf

Nanoporous BiVO4 Photoanodes with Dual-Layer Oxygen Evolution Catalysts for Solar Water Splitting

Design of one-dimensional submicron periodic gratings in thin-film silicon solar cells is investigated by rigorous full-wave analysis. Photocurrent densities are evaluated taking into account the non-conformal growth of the layers on the gratings.

Optical Analysis of Thin-Film Silicon Solar Cells on 1-D Periodic Gratings with Non-Conformal Layers

Inside Cover: Efficient Water-Splitting Device Based on a Bismuth Vanadate Photoanode and Thin-Film Silicon Solar Cells (ChemSusChem 10/2014)

Optical modelling and fabrication of hetero-junction c-Si nanowire solar cells is presented, including light propagation analysis and geometrical optimization. Performance of the fabricated device shows an unprecedented 11.8% conversion efficiency.

Radial heterojunction c-Si nanowire solar cells with 11.8% conversion efficiency

Investigation of Crystallinity Depth Profile in Thin Film µc-Si:H on Different Substrates

Performance limits of a heterojunction thin-film crystalline silicon on a glass solar cell (SC) in a substrate configuration were analyzed using the computer simulation program “Advanced Semiconductor Analysis” from the Delft University of Technology. The role of light trapping, due to scattering at randomly rough interfaces, on the absorption in the individual layers of the SC was investigated. The effect of the crystalline silicon absorber thickness, quality and passivation on the external parameters of the SC was evaluated. Using light trapping, the efficiency of an SC with 1- and 10-μm-thick c-Si absorber with a minority carrier lifetime of 10 -4 s and a surface recombination velocity of 10 -1m/s can achieve 13.8% and 17.8%, respectively.

http://ieeexplore.ieee.org/iel7/5503869/6596156/06555839.pdf

Miro Zeman

Papers

Optical Analysis of Thin-Film Silicon Solar Cells on 1-D Periodic Gratings with Non-Conformal Layers

Inside Cover: Efficient Water-Splitting Device Based on a Bismuth Vanadate Photoanode and Thin-Film Silicon Solar Cells (ChemSusChem 10/2014)

Radial heterojunction c-Si nanowire solar cells with 11.8% conversion efficiency

Investigation of Crystallinity Depth Profile in Thin Film µc-Si:H on Different Substrates

Performance Analysis of Thin-Film Crystalline Silicon-on-Glass Solar Cells