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

Selective adsorption of ethane from a mixture of ethane (C2H6) and ethylene (C2H4) has emerged as an energy-efficient process for obtaining high-purity ethylene. Recently, it has been reported that some novel microporous organometallic and organic adsorbents can preferentially adsorb C2H6 over C2H4. Conversely, zeolite adsorbents, which are widely used in industry due to their high stability and low material cost, generally prefer C2H4 adsorption (“olefin-philic”). In this study, we carefully investigated the effects of chemical composition (Si/Al ratio), silanol defect, and pore topology (BEA, CHA, and MFI) of zeolites to develop efficient “olefin-phobic” adsorbents. The results showed that the Si–O–(Na+)–Al (weak Lewis acid) and isolated Si–OH (weak Brønsted acid) groups in the zeolite frameworks undesirably increased the affinity for C2H4 (Lewis base). Consequently, defect-free pure silica zeolites exhibited promising C2H6/C2H4 selectivities (1.98–2.25), which were superior to those of Al-containing zeolites (0.26) and pure silica zeolites with abundant silanols (1.50), at 298 K and 1 bar. In particular, defect-free pure silica BEA exhibited the highest C2H6/C2H4 selectivity (2.25), large C2H6 uptake (2.27 mmol g–1), and facile regeneration at 298 K. The adsorbent enabled the efficient separation of high-purity C2H4 (>99.95%) from a mixture of C2H6/C2H4 with high productivity (22.98 L L–1). The productivity was comparable or even superior to that of recently reported C2H6-selective adsorbents. The present results provide hope for the development of efficient, stable, and scalable inorganic adsorbents for the selective C2H6 adsorption. 

Design of Olefin-Phobic Zeolites for Efficient Ethane and Ethylene Separation

Provided are a nanoporous organic polymer and preparation method thereof, and its application for catalyst. More particularly, provided is a nanoporous organic polymer composite comprising a mesoporous molecular sieve having micropores within mesopore walls, and an organic polymer impregnated within the micropores of the molecular sieve and coated on the wall surfaces of the molecular sieve. Also, provided is a method for preparing a nanoporous organic polymer composite comprising preparing a mesoporous molecular sieve having micropores within mesopore walls; impregnating an organic monomer diluted in solvent into the molecular sieve; and polymerizing the molecular sieve impregnated with the organic monomers to form organic polymers within the micropores and on the wall surfaces of the mesoporous molecular sieves. Further, provided are properties of catalytic reaction of the material as applicable representative examples of the nanoporous organic polymer.

Nanoporous organic polymer composite and preparation method thereof and its application for catalyst

Synergistic interactions between water and the metal/oxide interface in CO oxidation on Pt/CeO2 model catalysts

Structural Heterogeneity of Single-Atom Catalysts and True Active Site Generation Via Ligand Exchange During Electrochemical H2o2 Production

A method of forming the highly selective ultra-small pore amorphous adsorbent includes introducing an ion-exchange material to a sodium aluminosilicate zeolite such that an ion-exchanged zeolite forms, calcinating the ion-exchanged zeolite at a calcination temperature such that the ion-exchanged zeolite collapses and forms the decationized amorphous adsorbent, and introducing a back ion-exchange material to the decationized amorphous adsorbent such that the highly selective ultra-small pore amorphous adsorbent forms. The highly selective ultra-small pore amorphous adsorbent has a pore aperture size operable to permit carbon dioxide to adsorb into the amorphous adsorbent and operable to deny methane from adsorbing into the amorphous adsorbent.

Synthesis of ultra-small pore aluminosilicates by controlled structural collapse of zeolites

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