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

We have printed firing through silver paste on n+ polysilicon passivated layer structures deposited by Low Pressure Chemical Vapor Deposition (LPCVD). We analysed recombination at the metal contacts by photoluminescence imaging of metallised lifetime samples and found for the best paste, metal semiconductor recombination current density values (J0met) below 100 fA/cm2. To our knowledge, these are among the lowest values reported so far for full size M2 wafers with 150 nm thin polysilicon layer. On samples metallised with standard commercial pastes for diffused emitters, we observed higher J0met values, while contact resistivity was acceptable for all samples. We also studied the effect of the peak firing temperature on the J0met and contact resistivity in this work. Further, we compared the impact of deep and shallow doping profiles on the passivation and the J0met values.

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Screen printed Ag contacts for n-type polysilicon passivated contacts

Comparison of a-SiC:H and a-SiN:H as candidate materials for a p-i interface layer in a-Si:H p-i-n solar cells

A low-temperature synthesis of electrochemical active Pt nanoparticles and thin films by atomic layer deposition on Si(111) and glassy carbon surfaces

Influence of Polysilicon Thickness on Properties of Screen‑Printed Silver Paste Metallized Silicon Oxide/Polysilicon Passivated Contacts

One-dimensional photonic crystals having desired broad region of high reflectance ( R ) were fabricated by alternating the deposition of amorphous silicon and amorphous silicon nitride layers. The effect of the deposition temperature and angle of incidence on the optical properties of photonic crystals deposited on glass substrate was determined and an excellent matching was found with the simulated results. The broad region of high R of photonic crystals deposited on flat and textured ZnO:Al substrates decreases when compared to the R of photonic crystals de-posited on glass. The performance of amorphous silicon solar cells with 1-D photonic crystals integrated as the back reflector was evaluated. The external quantum efficiency measurement demonstrated that the solar cells with the photonic crystals back reflector had an enhanced re-sponse in the long wavelength region (above 550 nm) compared to the cells with the Ag reflector.

Miro Zeman

Papers

Screen printed Ag contacts for n-type polysilicon passivated contacts

Comparison of a-SiC:H and a-SiN:H as candidate materials for a p-i interface layer in a-Si:H p-i-n solar cells

A low-temperature synthesis of electrochemical active Pt nanoparticles and thin films by atomic layer deposition on Si(111) and glassy carbon surfaces

Influence of Polysilicon Thickness on Properties of Screen‑Printed Silver Paste Metallized Silicon Oxide/Polysilicon Passivated Contacts

Photonic Crystal Back Reflector in Thin-film Silicon Solar Cells