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

/pdf/studies-in-surface-science-and-catalysis-2ogdlcr44y.pdf

Studies in Surface Science and Catalysis

A review of vapor grown carbon nanofiber/polymer conductive composites

Sensors and actuators based on carbon nanotubes and their composites: A review

Electrocatalysis at graphite and carbon nanotube modified electrodes: edge-plane sites and tube ends are the reactive sites

Carbon nanofibers are described as a new ultrahigh-strength material, which is superior to both ordinary carbon fibers and other high-strength materials. The place occupied by nanofibers in the classification of carbon materials is shown, and an analysis is made of the relationship between the structure of a fiber and its useful properties, in particular, the strength and tensile modulus. Studies on the synthesis of nanofibers are reviewed. It is shown that the practically important problem of producing nanofibers of maximum possible length must be solved by controlling the temperature conditions of the reaction. The prospects for introducing nanofibers into the market of high-strength and heat-resistant materials are analyzed. The most likely prospect seems to be the partial replacement of polyacrylonitrile-based fibers by nanofibers, first and foremost, in the fields where the requirements for high strength are particularly stringent due to safety reasons.

Carbon Nanofibers: A New Ultrahigh-Strength Material for Chemical Technology

It has been shown that carbon blacks produced by iron carbonyl-catalyzed CO 2 -laser pyrolysis of benzene (laser pyrolysis carbon blacks) are characterized by a two-level nanostructure, i.e., they consist of amorphous carbon nanoparticles 30-40 nm in size and fullerene molecules where the fullerenes are predominantly represented by C 60 . Heat treatment of the blacks at 3000°C causes restructurization with the appearance of fullerene-like multishell nanoparticles of ∼20 nm in size, higher fullerenes, and multishell fullerenes. Unlike classical fullerenes, which have a cage structure and are known to have been synthesized in a variety of sizes (C 60 , C 70 , C 84 , C 102 , etc.), multishell fullerenes have a cage-inside-cage structure. Direct transmission electron microscopy observation of the cage-inside-cage clusters shows the occurrence of at least three varieties: two-shell 14-A-sized C 60 @C 240 , two-shell 20-A-sized (C 240 @C 560 ), and also three-shell 20-A-sized (C 80 @C 240 @C 560 ).

The observation of large concentric shell fullerenes and fullerene-like nanoparticles in laser pyrolysis carbon blacks

The combinatorial method, which was exclusively employed for the drug discovery until recently, has invaded the field of inorganic materials and is becoming a key technology in materials science today. Phosphors, with their diversity of possible mechanisms of luminescence, represent a typical example of a field where the combinatorial approach promises to be especially fruitful. Here, we present the results of systematic combinatorial exploration of different binary and ternary ZnO:dopant systems, which resulted in identification of bright luminescence in ZnO:(Y,Eu), ZnO:V, ZnO:W, and ZnO:(W,Mg) systems. Careful “zooming in”, i.e., fabrication and screening of more detailed libraries near the identified promising compositions, allowed us to find optimum phosphor compositions for the above-mentioned systems. The efficiency of the new phosphors in low-voltage cathodoluminescence is high and promises their prospective use in advanced flat panel display and lighting applications.

Vladimir Z. Mordkovich

Papers

Carbon Nanofibers: A New Ultrahigh-Strength Material for Chemical Technology

The observation of large concentric shell fullerenes and fullerene-like nanoparticles in laser pyrolysis carbon blacks

Discovery and Optimization of New ZnO-Based Phosphors Using a Combinatorial Method†

Intercalation into carbon nanotubes

Synthesis and XPS investigation of superdense lithium-graphite intercalation compound, LiC2