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

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.

http://science.sciencemag.org/content/sci/297/5582/787.full.pdf

Carbon Nanotubes--the Route Toward Applications

The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Signaling Recognition Events with Fluorescent Sensors and Switches.

Metal halide perovskites exhibit a rich crystal structure, with multiple phases as well as ferroelastic domains, which is crucial for the optical and electrical properties. The average crystal phase-transition temperatures can be shifted by size, strain, or defects, but it is not clear whether such differences can also appear locally within a single crystal. The experimental study of domain dynamics within nanocrystals is challenging and requires a method capable of probing crystal lattice variations with both high spatial and temporal resolution. Here, we show that in situ full-field diffraction x-ray microscopy can be used to image domains in a single crystal ${\mathrm{CsPbBr}}_{3}$ nanoplatelet as the temperature traverses the orthorhombic to tetragonal phase transition, at 150 nm spatial resolution and 6 s time resolution. The images reveal sudden domain pattern changes faster than the temporal resolution. Surprisingly, we observe substantial local variations during heating, with domain changes occurring at different temperatures within the single crystal. The nanoplatelet exhibits a high-temperature domain pattern completely different from the low-temperature one, but both patterns are reproducible, and we reversibly switch between them in multiple cycles. These results demonstrate that single ${\mathrm{CsPbBr}}_{3}$ crystals can exhibit substantial local variation of their basic crystal properties. 

In situ
 imaging of temperature-dependent fast and reversible nanoscale domain switching in a single-crystal perovskite

In this work we present preliminary results from molecular dynamics simulations for carbon nanotubes serpentine dynamics formation These S-like nanostructures consist of a series of parallel and straight nanotube segments connected by alternating U-turn shaped curves Nanotube serpentines were experimentally synthesized and reported in recent years, but up to now no atomistic simulations have been carried out to address the dynamics of formation of these structures We have carried out fully atomistic molecular dynamics simulations in the framework of classical mechanics with a standard molecular force field Multi-million atoms structures formed by stepped substrates with a carbon nanotube (about 1 micron in length) placed on top of them have been considered in our simulations A force is applied to the upper part of the tube during a short period of time and then turned off and the system set free to evolve in time Our results showed that these conditions are sufficient to form robust serpentines and validate the general features of the ‘falling spaghetti mechanism’ previously proposed to explain their formation

On the Formation of Carbon Nanotube Serpentines: Insights from Multi-Million Atom Molecular Dynamics Simulation

Dispositifs à base de fil nanométrique, réseaux, et leur procédés de fabrication

Nanoskopischen Draht enthaltende Anordnung, logische Felder und Verfahren zu deren Herstellung

Characterization of Rose Bengal-N,N′-Dimethyl-4,4′-bipyridinium Complexes and Their Separation in Aqueous SiO2 Colloids: Photophysical Properties of Rose Bengal in the Microheterogeneous System.

Ernesto Joselevich

Papers

In situ imaging of temperature-dependent fast and reversible nanoscale domain switching in a single-crystal perovskite

On the Formation of Carbon Nanotube Serpentines: Insights from Multi-Million Atom Molecular Dynamics Simulation

Dispositifs à base de fil nanométrique, réseaux, et leur procédés de fabrication

Nanoskopischen Draht enthaltende Anordnung, logische Felder und Verfahren zu deren Herstellung

Characterization of Rose Bengal-N,N′-Dimethyl-4,4′-bipyridinium Complexes and Their Separation in Aqueous SiO2 Colloids: Photophysical Properties of Rose Bengal in the Microheterogeneous System.