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

Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Recent years have seen a renewed interest in the harvesting and conversion of solar energy. Among various technologies, the direct conversion of solar to chemical energy using photocatalysts has received significant attention. Although heterogeneous photocatalysts are almost exclusively semiconductors, it has been demonstrated recently that plasmonic nanostructures of noble metals (mainly silver and gold) also show significant promise. Here we review recent progress in using plasmonic metallic nanostructures in the field of photocatalysis. We focus on plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks, and recently reported plasmon-mediated photocatalytic reactions on plasmonic nanostructures of noble metals. We also discuss the areas where major advancements are needed to move the field of plasmon-mediated photocatalysis forward.

Plasmonic-metal nanostructures for efficient conversion of solar to chemical energy

Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

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Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

Localized Surface Plasmon Resonance Sensors

Recent mechanistic insight into the synthesis of metal nanostructures by attachment-based growth is highlighted in this review. From quasi-spherical particles to nanowires, nanodendrites, and heterostructures built from nanoparticles as primary building blocks, the principles of oriented and misoriented attachment of metal nanoparticles are discussed within the context of diverse synthetic conditions. From this survey, a greater understanding of this growth mechanism emerges to provide general, and potentially greener, principles for the synthesis of advanced metal nanostructures, including those with applications in catalysis.

Attachment-based growth: building architecturally defined metal nanocolloids particle by particle

Metal nanoparticles (NPs) are of interest for applications in catalysis, electronics, chemical sensing, and more. Their utility is dictated by their composition and physical parameters such as particle size, particle shape, and overall architecture (e.g., hollow vs. solid). Interestingly, the addition of a second metal to create bimetallic NPs adds multifunctionality, with new emergent properties common. However, synthesizing structurally defined bimetallic NPs remains a great challenge. One synthetic pathway to architecturally controlled bimetallic NPs is seed-mediated co-reduction (SMCR) in which two metal precursors are simultaneously co-reduced to deposit metal onto shape-controlled metal seeds, which direct the overgrowth. Previously demonstrated in a Au–Pd system, here SMCR is applied to a system with a larger lattice mismatch between the depositing metals: Pd and Cu (7% mismatch for Pd–Cu vs. 4% for Au–Pd). Through manipulation of precursor reduction kinetics, the morphology and bimetallic distribution of the resultant NPs can be tuned to achieve eight-branched Pd–Cu heterostructures with Cu localized at the tips of the Pd nanocubes as well as branched Pd–Cu alloyed nanostructures and polyhedra. Significantly, the symmetry of the seeds can be transferred to the final nanostructures. This study expands our understanding of SMCR as a route to structurally defined bimetallic nanostructures and the synthesis of multicomponent nanomaterials more generally.

Seed-mediated co-reduction in a large lattice mismatch system: synthesis of Pd-Cu nanostructures.

https://pubs.acs.org/doi/pdf/10.1021/acs.chemmater.6b00472

Going with the Flow: Continuous Flow Routes to Colloidal Nanoparticles

Synthesis of hollow and trimetallic nanostructures by seed-mediated co-reduction

Crystal growth theory predicts that heterogeneous nucleation will occur preferentially at defect sites, such as the vertices rather than the faces of shape-controlled seeds. Platonic metal solids are generally assumed to have vertices with nearly identical chemical potentials, and also nearly identical faces, leading to the useful generality that heterogeneous nucleation preserves the symmetry of the original seeds in the final product. Herein, we test the limits of this generality in the extreme of low supersaturation, in an effort to expand the methods available for inducing anisotropic overgrowth. We formulate a strategy for favoring localized deposition that differentiates between both different vertices and different edges or faces, i.e., regioselective deposition. Deposition followed a simple kinetic model for nucleation rate, depending on wetting, supersaturation, and temperature. We demonstrate our ability to independently study the effects of varying supersaturation and surface passivation. Regio...

Sara E. Skrabalak

Papers

Attachment-based growth: building architecturally defined metal nanocolloids particle by particle

Seed-mediated co-reduction in a large lattice mismatch system: synthesis of Pd-Cu nanostructures.

Going with the Flow: Continuous Flow Routes to Colloidal Nanoparticles

Synthesis of hollow and trimetallic nanostructures by seed-mediated co-reduction

Surface Passivation and Supersaturation: Strategies for Regioselective Deposition in Seeded Syntheses