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

https://onlinelibrary.wiley.com/doi/pdf/10.1002/solr.202100478

A Comprehensive Workflow for High Resolution 3D Solar Photovoltaic (PV) Potential Mapping in Dense Urban Environment: A Case Study on Campus of Delft University of Technology

Photoluminescence properties of a-Si:H based thin films and corresponding solar cells

Nanostructure Analysis of P-Doped Nanocrystalline Silicon Oxide

We investigate the use of silver nanoparticles as light scattering elements to improve light trapping in amorphous silicon solar cells. Simulations presented in literature show that these nanoparticles can scatter light very efficiently due to plasmon resonance. However, our previous experimental work showed that light trapping does not improve when silver nanoparticles, fabricated by annealing a thin silver film, are embedded in a-Si:H solar cells. To shed some light on this we investigate the optical properties of these nanoparticles in more detail. Silver nanoparticle films with a mass thickness ranging from 3 to 18 nm were fabricated, resulting in films with average particle sizes ranging from 20 to 120 nm. We found that in all cases less than 10% of the incident light is scattered. The undesired absorption of light by the silver nanoparticles is at least three times stronger than the desired light scattering effect. We tentatively attribute this to the wide size distribution and high surface coverage inherent to this particle fabrication technique. We use an effective medium approach to incorporate the experimentally obtained optical properties of the nanoparticle films into our opto-electrical device simulator. This allows us to use realistic optical properties in solar cell simulations. We focus on a solar cell design with the silver nanoparticles embedded in a transparent conductive oxide layer at the rear of the a-Si:H layer. The solar cell simulations show that light trapping does not improve as long as absorption dominates over scattering. The simulated quantum efficiency curves are in agreement with experimental results.

Silver nanoparticles for plasmonic light trapping in A-Si:H solar cells

Advanced light management in thin-film solar cells is important in order to improve the photo-current and, thus, to raise up the conversion efficiencies of the solar cells. In this article two types of periodic structures iV one-dimensional diffraction gratings and photonic crystals,are analyzed in the direction of showing their potential for improved light trapping in thin-film silicon solar cells. The anti-reflective effects and enhanced scattering at the gratings with the triangular and rectangular features are studied by means of two-dimensional optical simulations. Simulations of the complete microcrystalline solar cell incorporating the gratings at all interfaces are presented. Critical optical issues to be overcome for achieving the performances of the cells with the optimized randomly textured interfaces are pointed out. Reflectance measurements for the designed 12 layer photonic crystal stack consisting of amorphous silicon nitride and amorphous silicon layers are presented and compared with the simulations. High reflectance (up to 99 %) of the stack is measured for a broad wavelength spectrum. By means of optical simulations the potential for using a simple photonic crystal structure as a back reflector in an amorphous silicon solar cell is demonstrated.

Miro Zeman

Papers

A Comprehensive Workflow for High Resolution 3D Solar Photovoltaic (PV) Potential Mapping in Dense Urban Environment: A Case Study on Campus of Delft University of Technology

Photoluminescence properties of a-Si:H based thin films and corresponding solar cells

Nanostructure Analysis of P-Doped Nanocrystalline Silicon Oxide

Silver nanoparticles for plasmonic light trapping in A-Si:H solar cells

Periodic Structures for Improved Light Management in Thin-film Silicon Solar Cells