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

With the development of science and technology, microelectronic components have evolved to become increasingly integrated and miniaturized. As a result, thermal management, which can seriously impact the function, reliability, and lifetime of such components, has become a critical issue. Recently, the use of polymer-based thermal interface materials (TIMs) in thermal management systems has attracted considerable attention in view of the superior comprehensive properties of the former. Compared with designing and fabricating a polymer with an intrinsically high thermal conductivity, a more effective and widely used strategy for improving the heat conductivity is to fill a polymer matrix with a thermally conductive filler. Specifically, three-dimensional (3D) interconnected heat-conductive networks can increase the thermal conductivity (k) of polymers more effectively than dispersed fillers can, owing to their intrinsic continuous structures. In this review, we first introduce the heat conduction mechanisms and the problems associated with polymer-based TIMs fabricated using engineering polymer chains and traditional filling methods. Next, we discuss the advantages and mechanisms of 3D interconnected heat-conductive networks for preparing thermally conductive polymer-based composites. In addition, we highlight new advancements in the design and fabrication of 3D thermally conductive networks as well as their application in improving the k of polymers. Our exhaustive review of 3D interconnected networks includes graphene, carbon nanotubes, boron nitride, metal and other 3D hybrid architectures. The key structural parameters and control methods for improving the thermal properties of polymer composites are outlined. Finally, we summarize some effective strategies and possible challenges for the development of polymer-based thermally conductive composites via integration with 3D interconnected networks.

Three-dimensional interconnected networks for thermally conductive polymer composites: Design, preparation, properties, and mechanisms

Liquid-infused surfaces (or lubricant-infused surfaces) (LIS) are a new class of functional materials introduced in 2011. Their exceptional properties have earned them a place at the forefront of many fields including anti-biofouling, anti-icing, anti-corrosion, drag reduction, droplet manipulation and drop-wise condensation. Integral to their success is the infused lubricant layer which affords them their properties. In this review, we examine the current state of the literature relating to the lubricant layer. We consider the lubricant through all stages in the surface's lifecycle from design, to use, all the way through to depletion and eventual failure. First, we examine trends in lubricant choice and how to choose a lubricant, including environmental and medical considerations. We then look at the different methods used to infuse lubricant into surfaces and how lubricant depletes from the surface. We then report direct and indirect methods to characterise the thickness and distribution of the lubricant layer. Finally, we examine how droplets interact with LIS and the unique properties afforded by the lubricant before providing an outlook into where research centred on understanding the lubricant layer is heading in the new decade.

Life and death of liquid-infused surfaces: a review on the choice, analysis and fate of the infused liquid layer.

Definitions and basic properties of the Voronoi diagram generalizations of the Voronoi diagram algorithms for computing Voronoi diagrams poisson Voronoi diagrams spatial interpolation models of spatial processes point pattern analysis locational optimization through Voronoi diagrams.

Spatial tessellations. Concepts and Applications of Voronoi diagrams

Carbon nanotubes (CNTs) with well aligned, highly regular structures possess advanced properties like high crystalline orientation and low thermal interface resistance. These properties enable them to become effective thermal interface materials (TIMs) in thermal management. However, the application is constrained by their fragility in the external environment. Additionally, air gaps and defects make aligned CNTs a poor thermally conducting model. Therefore, aligned CNT/polymer composites have been widely developed to acquire the combination of high thermal conductivity and other excellent properties. There are still some challenges which require further studies on improving the CNT quality, enhancing the interfacial strength and reducing the interface thermal resistance. This paper reviews recent progress in the thermal conduction of CNTs and their polymer composites. The synthesis methods are discussed along with the thermal conducting property dependence on the aligned CNT structure and morphology as well as the interface properties in details.

Thermal conducting properties of aligned carbon nanotubes and their polymer composites

Layered manganese metal-organic framework with high specific and areal capacitance for hybrid supercapacitors

Delivering liquid through the void spaces in porous metals is a daunting challenge for a variety of emerging interface technologies ranging from battery electrodes to evaporation surfaces. Hydraulic transport characteristics of well-ordered porous media are governed by the pore distribution, porosity, and morphology. Much like energy transport in polycrystalline solids, hydraulic transport in semi-ordered porous media is predominantly limited by defects and grain boundaries. Here, we report the wicking performances for porous copper inverse opals having pore diameters from 300 to 1000 nm by measuring the capillary-driven liquid rise. The capillary performance parameter within single crystal domain (K
 ij
 /R
 eff
  = 10−3 to 10−2 µm) is an order of magnitude greater than the collective polycrystal (K
 eff
 /R
 eff
  = ~10−5 to 10−3 µm) due to the hydraulic resistances (i.e. grain boundaries between individual grains). Inspired by the heterogeneity found in biological systems, we report that the capillary performance parameter of gradient porous copper (K
 eff
 /R
 eff
  = ~10−3 µm), comparable to that of single crystals, overcomes hydraulic resistances through providing additional hydraulic routes in three dimensions. The understanding of microscopic liquid transport physics through porous crystals and across grain boundaries will help to pave the way for the spatial design of next-generation heterogeneous porous media.

/pdf/microscale-liquid-transport-in-polycrystalline-inverse-opals-1lc5ce8jsf.pdf

Microscale Liquid Transport in Polycrystalline Inverse Opals across Grain Boundaries.

A recent design approach in creating super-repellent surfaces through slippery surface lubrication offers tremendous liquid-shedding capabilities. Previous investigations have provided significant insights into droplet–lubricant interfacial behaviors that govern antiwetting properties but have often studied using macroscale droplets. Despite drastically different governing characteristics of ultrasmall droplets on slippery lubricated surfaces, little is known about the effects at the micro- and nanoscale. In this investigation, we impregnate a three-dimensionally, well-ordered porous metal architecture with a lubricant to confirm durable slippery surfaces. We then reduce the droplet size to a nanoliter range and experimentally compare the droplet behaviors at different length scales. By experimentally varying the lubricant thickness levels, we also reveal that the effect of lubricant wetting around ultrasmall droplets is intensely magnified, which significantly affects the transient droplet dynamics. Mole...

Droplets on Slippery Lubricant-Infused Porous Surfaces: A Macroscale to Nanoscale Perspective.

Self-assembly continuously gains attention as an excellent method to create novel nanoscale structures with a wide range of applications in photonics, optoelectronics, biomedical engineering, and heat transfer applications. However, self-assembly is governed by a diversity of complex interparticle forces that cause fabricating defectless large scale (>1 cm) colloidal crystals, or opals, to be a daunting challenge. Despite numerous efforts to find an optimal method that offers the perfect colloidal crystal by minimizing defects, it has been difficult to provide physical interpretations that govern the development of defects such as grain boundaries. This study reports the control over grain domains and intentional defect characteristics that develop during evaporative vertical deposition. The degree of particle crystallinity and evaporation conditions is shown to govern the grain domain characteristics, such as shapes and sizes. In particular, the grains fabricated with 300 and 600 nm sphere diameters can be tuned into single-column structures exceeding ≈1 mm by elevating heating temperature up to 93 °C. The understanding of self-assembly physics presented in this work will enable the fabrication of novel self-assembled structures with high periodicity and offer fundamental groundworks for developing large-scale crack-free structures.

The Control of Colloidal Grain Boundaries through Evaporative Vertical Self-Assembly.

1 Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA 22904-4746, USA Department of Mechanical and Aerospace Engineering, University of California-Irvine, Irvine, CA 92697, USA Centro Tecnol ogico da Marinha em S~ao Paulo, Av. Prof. Lineu Prestes, 2468, Cidade Universit aria, S~ao Paulo 05508-000, SP, Brazil 4 Sandia National Laboratories, P.O. Box 5800 Box 5800, Albuquerque, New Mexico 87185, USA 5 School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China

Quang N. Pham

Papers

Layered manganese metal-organic framework with high specific and areal capacitance for hybrid supercapacitors

Microscale Liquid Transport in Polycrystalline Inverse Opals across Grain Boundaries.

Droplets on Slippery Lubricant-Infused Porous Surfaces: A Macroscale to Nanoscale Perspective.

The Control of Colloidal Grain Boundaries through Evaporative Vertical Self-Assembly.

Effect of growth temperature on the synthesis of carbon nanotube arrays and amorphous carbon for thermal applications