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

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Metal Oxides and Oxysalts as Anode Materials for Li Ion Batteries

Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields.

Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications

Transparent conductors as solar energy materials: A panoramic review

The authors describe the production of electrets prepared at ambient temperature in a dual-mode microwave/radiofrequency plasma reactor on single-crystal silicon substrates. They consist of 0.5-1.5- mu m-thick films of plasma silicon dioxide, plasma silicon nitride, plasma polymerized hexamethyldisilazane (pp-HMDSN), or a multilayer structure of these materials. The electret characteristics can be controlled by varying the plasma parameters and by a subsequent heat treatment, followed by a HMDSN-vapor surface modification. In order to characterize the charge storage capability, the samples were positively or negatively corona-charged and the charge decay was observed by measuring the surface potential at different temperatures. In addition, thermally stimulated current spectra were measured to obtain information about the activation processes. >

Charge storage in plasma deposited thin films

Thin films deposited by nonequilibrium processes, such as in low pressure plasmas, are sensitive to aging due to the presence of free radicals, dangling bonds, defects, voids, internal stress and other features. Generally, several aspects of film stability or aging can be considered: 

A:

spontaneous aging — internal material property characterized by the driving force to acquire minimum system energy without any intermediate agent;




B:

environmental aging — reaction with the ambient atmosphere (not “deliberately severe”);




C:

accelerated aging — post deposition treatment (deliberately severe) using various thermal, chemical, radiative, mechanical and other agents.

Aging Processes in Diamond-Like Carbon and Carbon/Metal Films

Ta-C micro-composite material formed by heat treatment of plasma carburized layer

Core-shell slanted nanocolumnar thin films (SCTFs) were produced by e-beam glancing angle deposition of SiO2 and subsequent atomic layer deposition (ALD) of TiN. Conformity of the ALD film over the slanted columns was confirmed by transmission electron microscopy and energy dispersive X-ray spectroscopy mappings. Angle resolved spectrophotometry characterization revealed angle-dependent transmission of the films, akin to their fully metallic counterparts. We found that such inclined core-shell nanocolumn films enable tailoring of the angular selectivity independently from the SCTF thickness and density.

Tailoring angular selectivity in SiO2 slanted columnar thin films using atomic layer deposition of titanium nitride

A dual-frequency deposition approach is discussed which consists of a microwave discharge during which an RF-induced negative DC bias voltage V/sub B/ is applied to the substrates. This permits one to control the flux and energy of the ions bombarding the growing films, offering the possibility of tailoring the film microstructure and composition, and maintaining a high deposition rate (10-100 AA/s) while keeping the substrate temperature low. The effects of V/sub B/ on the electrical properties of various thin film materials are reported. Hydrogenated amorphous silicon, plasma silicon nitride, plasma silicon oxide, and oxynitride, and plasma polymerized hexamethyl-disiloxane films were studied. The dual-frequency deposition technique has proven to be a powerful approach for fabrication of high-quality dielectric and semiconducting thin-film materials. >

Ludvik Martinu

Papers

Charge storage in plasma deposited thin films

Aging Processes in Diamond-Like Carbon and Carbon/Metal Films

Ta-C micro-composite material formed by heat treatment of plasma carburized layer

Tailoring angular selectivity in SiO2 slanted columnar thin films using atomic layer deposition of titanium nitride

Electrical properties of dual-frequency plasma deposited silicon-compound films