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

Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

1. INTRODUCTION Among the classes of highly porous materials, metalÀorganic frameworks (MOFs) are unparalleled in their degree of tunability and structural diversity as well as their range of chemical and physical properties. MOFs are extended crystalline structures wherein metal cations or clusters of cations (\" nodes \") are connected by multitopic organic \" strut \" or \" linker \" ions or molecules. The variety of metal ions, organic linkers, and structural motifs affords an essentially infinite number of possible combinations. 1 Furthermore, the possibility for postsynthetic modification adds an additional dimension to the synthetic variability. 2 Coupled with the growing library of experimentally determined structures, the potential to computationally predict, with good accuracy, affinities of guests for host frameworks points to the prospect of routinely predesigning frameworks to deliver desired properties. 3,4 MOFs are often compared to zeolites for their large internal surface areas, extensive porosity, and high degree of crystallinity. Correspondingly, MOFs and zeolites have been utilized for many of the same applications

Metal–Organic Framework Materials as Chemical Sensors

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Metal–organic frameworks (MOFs) are a unique class of crystalline solids comprised of metal cations (or metal clusters) and organic ligands that have shown promise for a wide variety of applications Over the past 15 years, research and development of these materials have become one of the most intensely and extensively pursued areas A very interesting and well-investigated topic is their optical emission properties and related applications Several reviews have provided a comprehensive overview covering many aspects of the subject up to 2011 This review intends to provide an update of work published since then and focuses on the photoluminescence (PL) properties of MOFs and their possible utility in chemical and biological sensing and detection The spectrum of this review includes the origin of luminescence in MOFs, the advantages of luminescent MOF (LMOF) based sensors, general strategies in designing sensory materials, and examples of various applications in sensing and detection

Luminescent metal–organic frameworks for chemical sensing and explosive detection

Accelerating the discovery of novel γ/γ' Co-based superalloys by probing temperature and alloying effects on the γ' precipitates

The diffusion couples of Co-Cr-Mo ternary alloys were prepared and annealed at 1473 K for 72 h in order to determine the interdiffusion coefficients by using the electron probe microanalysis combined with Whittle and Green method. The experimental interdiffusion coefficients were critically assessed to the atomic mobilities by means of DICTRA software package. Good agreements were obtained from comprehensive comparison between the model-predicted diffusion properties and the experimental data, meanwhile, considered that the calculated diffusion coefficients were within the acceptable uncertainty of the experimentally measured diffusion coefficients, which verified the reliability of the atomic mobilities. The diffusion phenomena, such as diffusion paths and the concentration-distance profiles in the Co-Cr-Mo ternary system can be reasonably described by the presently obtained atomic mobilities.

Interdiffusion and Atomic Mobilities in fcc Co-Cr-Mo Alloys

Two-photon absorption (TPA) of many chromophores can be enhanced by building them into the structure of metal–organic frameworks (MOFs). However, light scattering of MOFs defocuses the light beam a...

Metal–Organic Layers with an Enhanced Two-Photon Absorption Cross-Section and Up-Converted Emission

On the basis of three groups of Ti/Ti-10 at.% Ga and Ti/Ti-7 at.% Cu diffusion couples, respectively, interdiffusion coefficients in the bcc Ti-Ga and Ti-Cu binary alloys in the temperature range of 1273-1573 K were evaluated by means of the den Broeder method. Based on various reported experimental and the present measured diffusion coefficients as well as the available thermodynamic information, accurate atomic mobilities in the bcc Ti-Ga and Ti-Cu alloys were assessed via the DICTRA simulation package. A semi-empirical correlation was employed in the present work for the self-diffusivities in the hypothetical bcc Ga and Cu. Comparision between the calculated and measured diffusion coefficients indicated that most of the experimental information can be reasonably reproduced. The developed diffusion mobilities were further validated by the prediction of the concentration-distance profiles.

Interdiffusion and Atomic Mobilities in bcc Ti-Ga and Ti-Cu Alloys

The isothermal sections of the Al-Sn-Co ternary system at 800 °C and 1000 °C were constructed by twenty-nine key samples and two solid–liquid diffusion couples using electron probe microanalysis and x-ray diffraction analysis. The results show that: (1) No ternary intermetallic compound was found in this ternary system at 800 °C and 1000 °C. (2) The solid solubility of Sn in the Al-Co binary compounds is very small. (3) As-cast Al47Sn47Co6, Al46Sn46Co8 and Al45Sn45Co10 (at.%) alloys exhibit the separated macroscopic morphologies. The reason is that the addition of Co can significantly promote the metastable liquid-phase separation in Al-Sn binary system. The newly determined phase equilibria may contribute to thermodynamic assessment and development of Al-based alloys.

Cheng Wang

Papers

Accelerating the discovery of novel γ/γ' Co-based superalloys by probing temperature and alloying effects on the γ' precipitates

Interdiffusion and Atomic Mobilities in fcc Co-Cr-Mo Alloys

Metal–Organic Layers with an Enhanced Two-Photon Absorption Cross-Section and Up-Converted Emission

Interdiffusion and Atomic Mobilities in bcc Ti-Ga and Ti-Cu Alloys

Phase Equilibria in the Al-Sn-Co Ternary System