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

Ion Assisted Thin Film Growth in Dual Microwave/Radio Frequency Plasmas

Reliable control of the deposition process of optical films and coatings frequently requires monitoring of the refractive index profile throughout the layer. In the present work a simple in situ approach is proposed which uses a WKBJ matrix representation of the optical transfer function of a single thin film on a substrate. Mathematical expressions are developed which represent the minima and maxima envelopes of the curves transmittance-vs-time and reflectance-vs-time. The refractive index and extinction coefficient depth profiles of different films are calculated from simulated spectra as well as from experimental data obtained during PECVD of silicon-compound films. Variation of the deposition rate with time is also evaluated from the position of the spectra extrema as a function of time. The physical and mathematical limitations of the method are discussed.

A simple method for the determination of slowly varying refractive index profiles from in situ spectrophotometric measurements

The influence of the microstructure of strontium-titanate-oxide (SrTiO3 or STO) thin films on their optical properties was investigated through an extensive characterization. The STO films have been deposited on silicon substrates by reactive pulsed laser deposition. The effect of the oxygen deposition pressure on the crystalline quality of the films was systematically studied by x-ray diffraction and scanning electron microscopy. Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and secondary ion mass spectrometry were used to determine the atomic density and depth concentration profiles of the various species forming the film. The refractive index and extinction coefficient were obtained using variable angle spectroscopic ellipsometry. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their microstructural properties. In particular, the refractive index increases with film density, while losses decrease. In addition, the interface between STO and Si is characterized by an interdiffusion layer. As the deposition pressure is enhanced, the width of this layer significantly increases, inducing localized inhomogeneity of the refractive index.

Influence of the microstructure on the optical characteristics of SrTiO3 thin films

Amorphous fluorocarbon polymers are attractive materials for optical applications because of their high transparency at wavelengths up to 3 micrometers because of the absence of C-H bonds. since 1989 DuPont's amorphous fluoropolymer Teflon AF is available, films of which can be fabricated by means of spin, spray, or dip coating from solution or by use of compression or injection molding from the melt. An alternative and promissing route for processing fluorocarbon films is the use of a low- pressure plasma: This technique can be employed for plasma polymerization of suitable fluorocarbon monomers and for controlled etching of fluorocarbon materials. In the present work, we present the characteristics of plasma-polymerized tetrafluoroethylene layers with a refractive index of approximately 1.4. Reactive ion etching in an N2O plasma is used for patterning these layers, and also the spin-coated Teflon AF films with a refractive index of around 1.3. Possibilities of fabricating passive and active polymer waveguide devices from flurocarbon polymers are discussed, and estimates of the expected waveguide performance are presented.

Plasma-deposited fluorocarbon coatings for passive and active integrated optical devices

There is a continuous need for new hard and superhard (H > 40 GPa) materials for applications ranging from protective coatings for cutting tools and aerospace to automobile industries, MEMS and others. In this work nanocomposite hard coatings fabricated by plasma-enhanced chemical vapor deposition from TiCl4/SiH4/CH4/N2/H2/Ar gas mixtures were found to possess unique properties such as superhardness, high toughness, and interesting optical properties and colors. The mechanical characteristics such as hardness and Young’s modulus were determined by depth-sensitive indentation. Film microstructure was studied by XRD, SEM, TEM, ERD-TOF, XPS, and AFM. Optical properties like color, refractive index and extinction coefficient were evaluated using combined spectrophotometry and spectroscopic ellipsometry. This multitechnique approach allowed us to determine the structure-property relationships. We have shown that nc-TiN/a-Si3N4 exhibits a hardness of 45 GPa, while the novel nc-TiCN/a-SiCN provides a hardness of 57 GPa in addition to a very high resistance to plastic deformation (1.8 GPa).

Ludvik Martinu

Papers

Ion Assisted Thin Film Growth in Dual Microwave/Radio Frequency Plasmas

A simple method for the determination of slowly varying refractive index profiles from in situ spectrophotometric measurements

Influence of the microstructure on the optical characteristics of SrTiO3 thin films

Plasma-deposited fluorocarbon coatings for passive and active integrated optical devices

Mechanical and optical characteristics of superhard nanocomposite TiN/a-Si3N4 and TiCN/a-SiCN coatings produced by PECVD