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

The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

This review covers important advances in recent years in the physics of thin-film ferroelectric oxides, the strongest emphasis being on those aspects particular to ferroelectrics in thin-film form. The authors introduce the current state of development in the application of ferroelectric thin films for electronic devices and discuss the physics relevant for the performance and failure of these devices. Following this the review covers the enormous progress that has been made in the first-principles computational approach to understanding ferroelectrics. The authors then discuss in detail the important role that strain plays in determining the properties of epitaxial thin ferroelectric films. Finally, this review ends with a look at the emerging possibilities for nanoscale ferroelectrics, with particular emphasis on ferroelectrics in nonconventional nanoscale geometries.

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Physics of thin-film ferroelectric oxides

Thermoelectrics have long been recognized as a potentially transformative energy conversion technology due to their ability to convert heat directly into electricity. Despite this potential, thermoelectric devices are not in common use because of their low efficiency, and today they are only used in niche markets where reliability and simplicity are more important than performance. However, the ability to create nanostructured thermoelectric materials has led to remarkable progress in enhancing thermoelectric properties, making it plausible that thermoelectrics could start being used in new settings in the near future. Of the various types of nanostructured materials, bulk nanostructured materials have shown the most promise for commercial use because, unlike many other nanostructured materials, they can be fabricated in large quantities and in a form that is compatible with existing thermoelectric device configurations. The first generation of these materials is currently being developed for commercialization, but creating the second generation will require a fundamental understanding of carrier transport in these complex materials which is presently lacking. In this review we introduce the principles and present status of bulk nanostructured materials, then describe some of the unanswered questions about carrier transport and how current research is addressing these questions. Finally, we discuss several research directions which could lead to the next generation of bulk nanostructured materials.

Bulk nanostructured thermoelectric materials: current research and future prospects

The conversion efficiency of heat to electricity in thermoelectric materials depends on both their thermopower and electrical conductivity. It is now reported that, unlike their inorganic counterparts, organic thermoelectric materials show an improvement in both these parameters when the volume of dopant elements is minimized; furthermore, a high conversion efficiency is achieved in PEDOT:PSS blends.

Engineered doping of organic semiconductors for enhanced thermoelectric efficiency

Epitaxial 0%, 3% and 10% La doped PZT capacitors with a LSCO bottom electrode grown by pulsed laser deposition on Si using a Ti(Al)N/Pt conducting barrier layer were systematically studied. Ferroelectric capacitors substituted with 10% La show a significantly lower coercive voltage compared to capacitors with 0% and 3% La. This is attributed to the systematic variation of the domain structure of the PLZT film with the increase of La concentration. The in-plane orientation relationship of this heterostructure is: [110]PLZT//[110]LSCO//[110]Pt//[110]Ti(AI)N[110]si. The morphology of the domains as a function of La concentration was studied using high resolution transmission electron microscopy(HREM). The Pt/Ti(Al)N conducting barrier layer stack is intact after the deposition of the LSCO/PLZT/LSCO stack. All Ti(Al)N layers in the samples studied consist of column-like structures with a [110] texture.

Microstructure Investigations and Structure-Property Correlations in Ferroelectric thin film Capacitors

We demonstrate a methodology using a laser-assisted scanning probe nanolithography (LASPN) technique to generate organized nanostructures. Experimental approach combined with finite element analysis was utilized to study the interfacial interactions between a gold-coated probe of an atomic force microscope and a single crystal silicon substrate. Research results proved that the tip temperature had been raised via LASPN to 900 K at a laser power of 12 mW. Nanolines were formed during sliding while the silicon substrate was heated at a laser power of 5 mW. We propose an energy model to explain the phenomenon. SCANNING 32: 327–335, 2010. © 2010 Wiley Periodicals, Inc.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/sca.20198

Stress-induced nanostructures through laser-assisted scanning probe nanolithography

The strategy of adding solid particles to fluids for improving thermal conductivity has been pursued for more than one century. Here, a novel concept of using liquid nanodroplets for enhancing thermal performance has been developed and demonstrated in polyalphaolefin nanoemulsion fluids with dispersed ethanol nanodroplets. The ethanol/polyalphaolefin nanoemulsion fluids are spontaneously generated by self-assembly, and are thermodynamically stable. Their thermophysical properties, including thermal conductivity and viscosity, and impact on convective heat transfer are investigated experimentally. The thermal conductivity enhancement in these fluids is found to be moderate, but increases rapidly with increasing temperature in the measured temperature range from 35 oC to 75 oC. A very remarkable increase in convective heat transfer coefficient occurs in the nanoemulsion fluids due to the explosive vaporization of the ethanol nanodroplets at the superheat limit (i.e., spinodal states, about 122 oC higher than the atmospheric boiling point for ethanol). The explosive liquid-vapor phase transition is monitored using high speed camera. The fluid heat transfer could be augmented through the heat of vaporization (which intuitively raises the base fluid specific heat capacity) and the fluid mixing induced by the sound waves. The development of such phase-changeable nanoemulsion fluids would open a new direction for thermal fluids studies.Copyright © 2009 by ASME

Bao Yang

Papers

Microstructure Investigations and Structure-Property Correlations in Ferroelectric thin film Capacitors

Stress-induced nanostructures through laser-assisted scanning probe nanolithography

Thermophysical Characteristics of Self-Assembled Ethanol/Polyalphaolefin Nanoemulsion Fluids

A "flared-end" gradient coil with outer-wall direct cooling for human brain imaging: A feasibility study.

Field-factory hybrid service mode and its resource scheduling method based on an enhanced MOJS algorithm