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

Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Understanding TiO2 photocatalysis: mechanisms and materials.

Synthesis of metal-organic frameworks (MOFs): routes to various MOF topologies, morphologies, and composites.

Metal Organic Frameworks in Biomedicine Patricia Horcajada,* Ruxandra Gref, Tarek Baati, Phoebe K. Allan, Guillaume Maurin, Patrick Couvreur, G erard F erey, Russell E. Morris, and Christian Serre* Institut Lavoisier, UMR CNRS 8180, Universit e de Versailles St-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France Facult e de Pharmacie, UMR CNRS 8612, Universit e Paris-Sud, 92296 Châtenay-Malabry Cedex, France Institut Charles Gerhardt Montpellier, UMR CNRS 5253, Universit e Montpellier 2, 34095 Montpellier cedex 05, France EaStChem School of Chemistry, University of St. Andrews Purdie Building, St Andrews, KY16 9ST U.K.

Metal-organic frameworks in biomedicine.

Deconstructing the Crystal Structures of Metal Organic Frameworks and Related Materials into Their Underlying Nets Michael O’Keeffe* and Omar M. Yaghi* Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States Center for Reticular Chemistry, Center for Global Mentoring, Department of Chemistry and Biochemistry, University of California Los Angeles, 607 Charles E. Young Dr. East, Los Angeles, California 90095, United States Graduate School of EEWS, Korea Advanced Institute of Science and Technology, Daejeon, Korea

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Deconstructing the crystal structures of metal-organic frameworks and related materials into their underlying nets.

Titanium is a very attractive candidate for MOFs due to its low toxicity, redox activity, and photocatalytic properties. We present here MIL-125, the first example of a highly porous and crystalline titanium(IV) dicarboxylate (MIL stands for Materials of Institut Lavoisier) with a high thermal stability and photochemical properties. Its structure is built up from a pseudo cubic arrangement of octameric wheels, built up from edge- or corner-sharing titanium octahedra, and terephthalate dianions leading to a three-dimensional periodic array of two types of hybrid cages with accessible pore diameters of 6.13 and 12.55 A. X-ray thermodiffractometry and thermal analysis show that MIL-125 is stable up to 360 °C under air atmosphere while nitrogen sorption analysis indicates a surface area (BET) of 1550 m2·g−1. Moreover, under nitrogen and alcohol adsorption, MIL-125 exhibits a photochromic behavior associated with the formation of stable mixed valence titanium-oxo compounds. The titanium oxo cluster are back ox...

A New Photoactive Crystalline Highly Porous Titanium(IV) Dicarboxylate

The strategy of introducing protecting groups in organic chemistry has enabled major progress in multistep synthesis. [ 1 , 2 ] We believe that applying such a powerful concept to the processing of porous materials could signifi cantly extend the range of their applications. In microelectronics, porous thin fi lms have been used to both increase microprocessor performance and reduce power consumption. The extendibility of this approach relies on the successful integration of highly porous materials (ultralowk , ULK) at ever smaller dimensions. As of today, materials with a dielectric constant ( k ) as low as 2.4 are commonly used in manufacturing. [ 3 ] However, below this dielectric constant, increased pore size and interconnectivity lead to high sensitivity to wet and dry processes, which ultimately results in device failure. Here, we show that the porous structure can be fi lled with an organic polymer, which then acts as a protective agent during the various aggressive processing steps. We have demonstrated the effi cacy of this approach using a highly porous ( k = 2.0) organosilicate dielectric fi lm. The fi lled composite fi lm was almost impervious to processing damage and its porosity was fully regenerated after integration, while the unprotected, porous fi lm suffered severe structural and physical damage. We believe that this protection strategy will facilitate the integration of materials at k < 2.4 in future electronic devices. [ 4 ] In addition, using this concept it is possible to selectively block pores of different size and/or further independently modify the external and internal thin-fi lm surfaces. Therefore, it holds great promise for the selective functionalization of porous materials in areas such as membranes, biosensors, and catalysis. [ 5 , 6 ]

Application of the Protection/Deprotection Strategy to the Science of Porous Materials

We explore the application of a high-temperature precursor delivery system for depositing high boiling point organosilicate precursors on plastics using atmospheric plasma. Dense silica coatings were deposited on stretched poly(methyl methacrylate), polycarbonate and silicon substrates from the high boiling temperature precursor, 1, 2-bis(triethoxysilyl)ethane, and from two widely used low boiling temperature precursors, tetraethoxysilane and tetramethylcyclotetrasiloxane. The coating deposition rate, molecular network structure, density, Young’s modulus and adhesion to plastics exhibited a strong dependence on the precursor delivery temperature and rate, and the functionality and number of silicon atoms in the precursor molecules. The Young’s modulus of the coatings ranged from 6 to 34 GPa, depending strongly on the coating density. The adhesion of the coatings to plastics was affected by both the chemical structure of the precursor and the extent of exposure of the plastic substrate to the plasma during...

Atmospheric plasma deposited dense silica coatings on plastics.

Increasing the porosity of oxycarbosilane dielectrics is a key approach to lower the interconnect signal delay and thus enable manufacturing of lower power consumption and higher performance microprocessors. However, this path leads to excessive dielectric process damage as the industry adapts procedures developed for dense and microporous insulators to mesoporous materials. Currently ultralow dielectric constant (k) materials cannot be integrated at the most aggressive pitch. Here, it is reported that the post porosity plasma protection enables the mitigation of process damage across a wide range of porosity regimes. The exponential increase in plasma damage with porosity when going from microporous k = 2.4 to mesoporous k = 1.8 is shown. Using the same range of materials, the strategy allows a reduction in process damage to a constant minimal level on both blanket wafers and patterned structures. The results demonstrate how the strategy can enable the extendibility of current materials and processes to future technology nodes.

Post Porosity Plasma Protection: Scaling of Efficiency with Porosity

In one exemplary embodiment, a method includes: providing a structure having a first layer overlying a substrate, where the first layer includes a dielectric material having a plurality of pores; applying a filling material to an exposed surface of the first layer; heating the structure to a first temperature to enable the filling material to homogeneously fill the plurality of pores; after filling the plurality of pores, performing at least one process on the structure; and after performing the at least one process, removing the filling material from the plurality of pores by heating the structure to a second temperature to decompose the filling material.

Theo J. Frot

Papers

A New Photoactive Crystalline Highly Porous Titanium(IV) Dicarboxylate

Application of the Protection/Deprotection Strategy to the Science of Porous Materials

Atmospheric plasma deposited dense silica coatings on plastics.

Post Porosity Plasma Protection: Scaling of Efficiency with Porosity

Homogeneous porous low dielectric constant materials