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

3.6.1. Polishing and Cleaning 2663 3.6.2. Vacuum and Heat Treatments 2664 3.6.3. Carbon Electrode Activation 2665 3.7. Summary and Generalizations 2666 4. Advanced Carbon Electrode Materials 2666 4.1. Microfabricated Carbon Thin Films 2666 4.2. Boron-Doped Diamond for Electrochemistry 2668 4.3. Fibers and Nanotubes 2669 4.4. Carbon Composite Electrodes 2674 5. Carbon Surface Modification 2675 5.1. Diazonium Ion Reduction 2675 5.2. Thermal and Photochemical Modifications 2679 5.3. Amine and Carboxylate Oxidation 2680 5.4. Modification by “Click” Chemistry 2681 6. Synopsis and Outlook 2681 7. Acknowledgments 2682 8. References 2682

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Advanced carbon electrode materials for molecular electrochemistry.

Surface modification of inorganic nanoparticles for development of organic–inorganic nanocomposites—A review

This paper describes the preparation, characterization, and electrochemical properties of reduced graphene sheet films (rGSFs), investigating especially their electrochemical behavior for several redox systems and electrocatalytic properties towards oxygen and some small molecules. The reduced graphene sheets (rGSs) are produced in high yield by a soft chemistry route involving graphite oxidation, ultrasonic exfoliation, and chemical reduction. Transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy clearly demonstrate that graphene was successfully synthesized and modified at the surface of a glassy carbon electrode. Several redox species, such as Ru(NH3)63+/2+, Fe(CN)63−/4−, Fe3+/2+ and dopamine, are used to probe the electrochemical properties of these graphene films by using the cyclic voltammetry method. The rGSFs demonstrate fast electron-transfer (ET) kinetics and possess excellent electrocatalytic activity toward oxygen reduction and certain biomolecules. In our opinion, this microstructural and electrochemical information can serve as an important benchmark for graphene-based electrode performances.

Preparation, Structure, and Electrochemical Properties of Reduced Graphene Sheet Films

Electrografting refers to the electrochemical reaction that permits organic layers to be attached to solid conducting substrates. This definition can be extended to reactions involving an electron transfer between the substrate to be modified and the reagent, but also to examples where a reducing or oxidizing reagent is added to produce the reactive species. These methods are interesting as they provide a real bond between the surface and the organic layer. Electrografting applies to a variety of substrates including carbon, metals and their oxides, but also dielectrics such as polymers. Since the 1980s several methods have been developed, either by reduction or oxidation, and some of them have reached an industrial stage. This critical review describes the methods that are used for electrografting, their mechanism, the formation and growth of the layers as well as their applications (742 references).

Electrografting: a powerful method for surface modification

The effects of alumina nanoparticle on the properties of an epoxy resin system

Electrodeposition and characterization of polypyrrole films on copper

A facile method for the preparation of thin-film carbon electrodes by electron beam evaporation onto highly doped silicon is presented. The physical and electrochemical properties of these films both before and after postdeposition pyrolysis are investigated. Raman spectroscopy establishes the amorphous structure of the nonpyrolyzed carbon films and confirms the formation of graphitic carbon after pyrolysis at 1000 °C. Scanning force microscopy reveals the root-mean-square roughness of nonpyrolyzed films to be ∼1 A, while pyrolyzed films exhibit an increased roughness of ∼4 A. The electrochemical behavior of the electrodes resembles glassy carbon, with measured heterogeneous electron-transfer rate constants among the highest measured for thin carbon films. These carbon film electrodes will potentially find applications in such fields as molecular electronics and scanning probe microscopy of adsorbed species.

Ultraflat carbon film electrodes prepared by electron beam evaporation.

With the recent advances in nanoscience, there is promoting interest in nano-sized reinforced polymers for high technology applications. Evaluations on the curing reaction of diglycidyl ether of bisphenol A (DGEBA) cured with 4,4′-diaminodiphenylmethane (DDM) in the presence of nano-alumina have been carried out using DSC and In situ FT-IR measurements. The results from calorimetry measurements showed that the loading level of 2 is the optimum alumina concentrations for DDM-based composite. Different kinetic models including n th order, the Kamal autocatalytic, and the modified Avrami equations have been tested and the results of kinetic analysis are presented just for the last model owing to the better fitting of the experimental data. The viscoelastic behavior of the cured composites is determined using DMA showing that the storage modulus and the T g of the composites are improved with the addition of nano-filler concentration. Results from SEM analyses revealed that the filler encourages the development of large particles in the resin matrix. Mechanical property measurement of the composites indicated that high flexural modulus has been attained with increasing concentration of nano-Al 2 O 3 .

Understanding the effect of nano-Al2O3 addition upon the properties of epoxy-based hybrid composites

The effects of cellulose nanofiber on the curing behavior, dynamic mechanical, and morphology properties of epoxy/diamine systems were investigated. The studies were conducted using an aliphatic triamine, diethylentriamine (Dien), and an aromatic diamine, diaminodiphenylmethan (DDM), as the curing agents in the presence of three different levels of 0.5, 2, and 5 phr of cellulose nanofiber. Calorimetry experiments were used to probe the changes in the reaction enthalpy and in the glass transition temperature ( T g ) as a function of the fiber concentration. The results showed that both the T g and the heat of reaction were increased with increasing the fiber concentration up to 2 phr. The experimental cure data obtained from in situ FT-IR measurements were used to evaluate the kinetic parameters using the modified Avrami theory of phase change. The results showed that the kinetic parameters were less sensitive to the epoxy composition. DMTA measurements showed that the storage modulus and the T g of the composites were dependant on the level of fiber loading. SEM studies revealed that a reasonable dispersion and adhesion have been achieved between the fiber and the epoxy matrix at low concentration of fiber. It is concluded that the fiber agglomerated at high concentration of cellulose fiber prevented the formation of a homogeneous mixture, thus resulting in weak thermal and mechanical properties.

Abbas Ali Rostami

Papers

The effects of alumina nanoparticle on the properties of an epoxy resin system

Electrodeposition and characterization of polypyrrole films on copper

Ultraflat carbon film electrodes prepared by electron beam evaporation.

Understanding the effect of nano-Al2O3 addition upon the properties of epoxy-based hybrid composites

Influences of cellulose nanofiber on the epoxy network formation