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

Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...

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The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment

The surface science of titanium dioxide

The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. So far, the main focus has been on fundamental physics and electronic devices. However, we believe its true potential lies in photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultrawideband tunability. The rise of graphene in photonics and optoelectronics is shown by several recent results, ranging from solar cells and light-emitting devices to touch screens, photodetectors and ultrafast lasers. Here we review the state-of-the-art in this emerging field.

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Graphene photonics and optoelectronics

It is experimentally demonstrated that an applied dc magnetic field can transform the optical Fr\'eedericksz transition in a nematic film from second order to first order. The results are in good agreement with theoretical predictions.

Observation of magnetic-field-induced first-order optical Fréedericksz transition in a nematic film.

We report the use of a dual‐frequency dye laser system to generate continuously tunable far‐infrared radiation over the frequency range from 20 to 190 cm−1. We have investigated both collinear (forward and backward) and noncollinear phase matching in LiNbO3 over most of this frequency range and forward collinear phase matching in ZnO, ZnS, CdS, and CdSe at selected frequencies.

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Phase‐matched far‐infrared generation by optical mixing of dye laser beams

Using the model of Oseen and de Vries, we show that phase matching of optical third-harmonic generation can be achieved in a cholesteric liquid crystal with the help of the lattice momentum. Many different collinear phase-matching conditions exist. In some cases, the phase-matched third harmonic is generated in the same direction as the fundamental, and in some other cases, it is generated in the opposite direction. In many other cases, phase-matched third-harmonic generation requires the simultaneous presence of fundamental waves propagating in opposite directions. Analogous to electron-electron interaction in a periodic lattice, these processes can be identified as coherent, normal, and umklapp third-harmonic-generation processes. Experiments using a mode-locked Nd laser as the fundamental source verify the existence of most of the predicted phase-matching conditions. Our results agree well with the theoretical predictions.

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Y. R. Shen

Papers

Observation of magnetic-field-induced first-order optical Fréedericksz transition in a nematic film.

Phase‐matched far‐infrared generation by optical mixing of dye laser beams

Study of Phase-Matched Normal and Umklapp Third-Harmonic- Generation Processes in Cholesteric Liquid Crystals

1998 Frank Isakson Prize Address Sum frequency generation for vibrational spectroscopy: applications to water interfaces and films of water and ice

Multimode Effects in Stimulated Raman Emission