There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Accelerating the discovery of advanced materials is essential for human welfare and sustainable, clean energy. In this paper, we introduce the Materials Project (www.materialsproject.org), a core program of the Materials Genome Initiative that uses high-throughput computing to uncover the properties of all known inorganic materials. This open dataset can be accessed through multiple channels for both interactive exploration and data mining. The Materials Project also seeks to create open-source platforms for developing robust, sophisticated materials analyses. Future efforts will enable users to perform ‘‘rapid-prototyping’’ of new materials in silico, and provide researchers with new avenues for cost-effective, data-driven materials design. © 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

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Commentary: The Materials Project: A materials genome approach to accelerating materials innovation

Li-ion battery materials: present and future

https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

Fluorophosphate cathodes with the chemical formula NaxV2(PO4)2O2yF3–2y (0 ≤ x ≤ 4, 0 ≤ y ≤ 1) are some of the few known sodium-ion cathode materials with the potential to be competitive with conventional lithium-ion cathodes. However, the experimentally accessible performance of the fluorophosphates remains limited, primarily due to the fact that only half of the theoretical capacity has been reversibly cycled. In this article, we review the extensive body of literature on the fluorophosphate class of sodium-ion cathodes and, in combination with our own ab initio model of the material, investigate the mechanisms underlying the sodium-extraction limitations in the NaxV2(PO4)2F3 (y = 0) fluorophosphate. Specifically, we focus on the potential to reversibly extract sodium beyond the 1 ≤ x ≤ 3 range. We find that this limitation arises from a combination of the high voltage of the V4+/5+ oxidation reaction associated with sodium extraction in the 0 ≤ x ≤ 1 region and a precipitous drop in sodium diffusivity n...

http://pubs.acs.org/doi/pdf/10.1021/acs.chemmater.6b01989

Structure and Dynamics of Fluorophosphate Na-Ion Battery Cathodes

Design principles for high transition metal capacity in disordered rocksalt Li-ion cathodes

Alexandra J. Toumar, Shyue Ping Ong, William Davidson Richards, Stephen Dacek, and Gerbrand Ceder Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093, USA (Received 15 May 2015; revised manuscript received 9 November 2015; published 11 December 2015)

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Vacancy Ordering in O3-Type Layered Metal Oxide Sodium-Ion Battery Cathodes

Inorganic solid-state ionic conductors with high ionic conductivity are of great interest for their application in safe and high-energy-density solid-state batteries. Our previous study reveals that the crystal structure of the ionic conductor Li7P3S11 contains a body-centered-cubic (bcc) arrangement of sulfur anions and that such a bcc anion framework facilitates high ionic conductivity. Here, we apply a set of first-principles calculations techniques to investigate A7P3X11-type (A = Li, Na; X = O, S, Se) lithium and sodium superionic conductors derived from Li7P3S11, focusing on their structural, dynamic and thermodynamic properties. We find that the ionic conductivity of Na7P3S11 and Na7P3Se11 is over 10 mS cm–1 at room temperature, significantly higher than that of any known solid Na-ion sulfide or selenide conductor. However, thermodynamic calculations suggest that the isostructural sodium compounds may not be trivial to synthesize, which clarifies the puzzle concerning the experimental problems in t...

/pdf/computational-prediction-and-evaluation-of-solid-state-59syvtclbd.pdf

Computational Prediction and Evaluation of Solid-State Sodium Superionic Conductors Na7P3X11 (X = O, S, Se)

Achieving a Li-ion conductivity in the solid state comparable to existing liquid electrolytes is challenging. A fundamental relationship between anion packing and ionic transport now reveals desirable structural attributes for Li-ion conductors.

William D. Richards

Papers

Structure and Dynamics of Fluorophosphate Na-Ion Battery Cathodes

Design principles for high transition metal capacity in disordered rocksalt Li-ion cathodes

Vacancy Ordering in O3-Type Layered Metal Oxide Sodium-Ion Battery Cathodes

Computational Prediction and Evaluation of Solid-State Sodium Superionic Conductors Na7P3X11 (X = O, S, Se)

Design Principles for Solid‐State Lithium Superionic Conductors