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

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Single-atom catalysis has arguably become the most active new frontier in heterogeneous catalysis. Aided by recent advances in practical synthetic methodologies, characterization techniques and computational modelling, we now have a large number of single-atom catalysts (SACs) that exhibit distinctive performances for a wide variety of chemical reactions. This Perspective summarizes recent experimental and computational efforts aimed at understanding the bonding in SACs and how this relates to catalytic performance. The examples described here illustrate the utility of SACs in a broad scope of industrially important reactions and highlight the advantages these catalysts have over those presently used. SACs have well-defined active centres, such that unique opportunities exist for the rational design of new catalysts with high activities, selectivities and stabilities. Indeed, given a certain practical application, we can often design a suitable SAC; thus, the field has developed very rapidly and afforded promising catalyst leads. Moreover, the control we have over certain SAC structures paves the way for designing base metal catalysts with the activities of noble metal catalysts. It appears that we are entering a new era of heterogeneous catalysis in which we have control over well-dispersed single-atom active sites whose properties we can readily tune. Single-atom catalysts are heterogeneous materials featuring active metals sites atomically dispersed on a surface. This Review describes methods by which we prepare and characterize these materials, as well as how we can tune their catalytic performance in a variety of important reactions.

Heterogeneous single-atom catalysis

Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed.

Carbon Materials for Chemical Capacitive Energy Storage

This work was aimed to evidence that substituted pyridine, 2,6-di-tert-butylpyridine, is a suitable probe for the quantitative investigation of the external acidity in hierarchically structured zeolites. The 2,6-di-tert-butylpyridine was too large to enter the micropores, even in wide pore zeolites, and nearly no sites in nonmesoporous zeolites were available. Accessibility studies of acid sites in zeolites TNU-9 and BEA involving quantitative IR measurements with hindered 2,6-di-tert-butylpyridine as a probe were performed. The extinction coefficients of the 1615 cm–1 diagnostic bands of 2,6-di-tert-butylpyridine interacting with Bronsted acid sites were determined. Lewis acid sites were not detected with the probe. The accessibility factor (AF) for the 2,6-di-tert-butylpyridine probe molecule was defined as the number of sites detected by adsorption of the dTBPy (external sites) divided by the total amount of acid sites in the studied zeolites as quantified by pyridine sorption. Upon desilication result...

2,6-Di-tert-butylpyridine Sorption Approach to Quantify the External Acidity in Hierarchical Zeolites

Spatial distribution, strength, and dealumination behavior of acid sites in nanocrystalline MFI zeolites and their catalytic consequences

Solid adsorbents including amine-functionalized porous materials and zeolites have been extensively investigated for post-combustion CO2 capture. Amine-functionalized porous materials have shown highly promising CO2 uptake in a wet flue gas, but suffer from significant amine deactivation due to urea formation under desorption conditions (e.g., desorption under 100% CO2 at >130 °C) of temperature swing adsorption (TSA) cycles. In contrast, purely inorganic zeolites are thermochemically stable but cannot adsorb CO2 from a wet flue gas because of the preferential H2O adsorption. In the present work, we synthesized an ethylenediamine-grafted Y zeolite, which can synergistically combine the strengths of both adsorbent systems. The amine groups can effectively capture CO2 in a wet flue gas, while the strongly co-adsorbed H2O within the hydrophilic zeolite micropores suppresses urea formation (dehydration reaction between amines and CO2) under desorption conditions according to Le Chatelier's principle. The organic–zeolite hybrid adsorbent retains working capacities higher than 1.1 mmol g−1 over 20 TSA cycles. Because the adsorbent is prepared from a commercially available zeolite, it is also highly cost efficient and suitable for mass production.

An ethylenediamine-grafted Y zeolite: a highly regenerable carbon dioxide adsorbent via temperature swing adsorption without urea formation

The effects of KOH activation on pore structure of ordered mesoporous carbons were analyzed by transmission electron microscopy, powder X-ray diffraction and argon adsorption. The activation led to remarkable increases in micropore volume and BET surface area up to 1.0 mL g−1 and 2700 m2 g−1, at the expense of the mesostructural order. The resultant carbons with various microporosity and mesoporosity were tested for room-temperature adsorption of hydrogen under high pressure. The adsorption data were analyzed in correlation with the varied carbon pore structures. The results showed that the hydrogen adsorption capacity increased approximately linearly with respect to micropore volume, or BET surface area, reaching a 2.5-times higher value when fully activated. However, the adsorption capacity at 100 atm (0.75 wt%) was still far below the US DOE target of 6.5 wt%. The extrapolation of our results to the carbon structure with the highest possible surface area could lead to no more than 2.5 wt%. This result suggests that chemisorption or other chemical storage methods should be combined with physisorption if carbon materials are considered for hydrogen storage.

Mesoporous carbons with KOH activated framework and their hydrogen adsorption

Suppressing irreversible catalyst deactivation is critical in heterogeneous catalysis. In particular, deactivation via sintering of active sites is a significant issue for reactions involving harsh reaction/regeneration conditions. In this work, we developed a PtGa/γ-Al2O3 alkane dehydrogenation catalyst with exceptionally high activity, selectivity, and long-term stability by markedly suppressing Pt sintering under harsh conditions (reaction/regeneration at >823 K). To stabilize Pt, physical and chemical stabilization strategies were synergistically combined. For the former, Pt was introduced during the synthesis of γ-Al2O3 via sol–gel chemistry, which can increase the interfacial contact between Pt and γ-Al2O3 due to the partial entrapment of Pt in γ-Al2O3. For the latter, atomically dispersed Ce was doped on γ-Al2O3, which can stabilize Pt via strong Pt–O–Ce interactions. Because of effective Pt stabilization, the catalyst showed remarkably steady activity and selectivity behaviors over the repeated re...

http://pubs.acs.org/doi/pdf/10.1021/acscatal.6b00329

Physicochemical Stabilization of Pt against Sintering for a Dehydrogenation Catalyst with High Activity, Selectivity, and Durability

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Minkee Choi

Author Tools

Chat about Author