1,582 research outputs found
Modeling friction: From nanoscale to mesoscale
The physics of sliding friction is gaining impulse from nanoscale and
mesoscale experiments, simulations, and theoretical modeling. This Colloquium
reviews some recent developments in modeling and in atomistic simulation of
friction, covering open-ended directions, unconventional nanofrictional
systems, and unsolved problems.Comment: 26 pages, 14 figures, Rev. Mod. Phys. Colloquiu
Dimensional crossover and incipient quantum size effects in superconducting niobium nanofilms
Superconducting and normal state properties of sputtered Niobium nanofilms
have been systematically investigated, as a function of film thickness in a
d=9-90 nm range, on different substrates. The width of the
superconducting-to-normal transition for all films remained in few tens of mK,
thus remarkably narrow, confirming their high quality. We found that the
superconducting critical current density exhibits a pronounced maximum, three
times larger than its bulk value, for film thickness around 25 nm, marking the
3D-to-2D crossover. The extracted magnetic penetration depth shows a sizeable
enhancement for the thinnest films, aside the usual demagnetization effects.
Additional amplification effects of the superconducting properties have been
obtained in the case of sapphire substrates or squeezing the lateral size of
the nanofilms. For thickness close to 20 nm we also measured a doubled
perpendicular critical magnetic field compared to its saturation value for d>33
nm, indicating shortening of the correlation length and the formation of small
Cooper pairs in the condensate. Our data analysis evidences an exciting
interplay between quantum-size and proximity effects together with
strong-coupling effects and importance of disorder in the thinnest films,
locating the ones with optimally enhanced critical properties close to the
BCS-BEC crossover regime
Recent progress in the JARVIS infrastructure for next-generation data-driven materials design
The Joint Automated Repository for Various Integrated Simulations (JARVIS)
infrastructure at the National Institute of Standards and Technology (NIST) is
a large-scale collection of curated datasets and tools with more than 80000
materials and millions of properties. JARVIS uses a combination of electronic
structure, artificial intelligence (AI), advanced computation and experimental
methods to accelerate materials design. Here we report some of the new features
that were recently included in the infrastructure such as: 1) doubling the
number of materials in the database since its first release, 2) including more
accurate electronic structure methods such as Quantum Monte Carlo, 3) including
graph neural network-based materials design, 4) development of unified
force-field, 5) development of a universal tight-binding model, 6) addition of
computer-vision tools for advanced microscopy applications, 7) development of a
natural language processing tool for text-generation and analysis, 8) debuting
a large-scale benchmarking endeavor, 9) including quantum computing algorithms
for solids, 10) integrating several experimental datasets and 11) staging
several community engagement and outreach events. New classes of materials,
properties, and workflows added to the database include superconductors,
two-dimensional (2D) magnets, magnetic topological materials, metal-organic
frameworks, defects, and interface systems. The rich and reliable datasets,
tools, documentation, and tutorials make JARVIS a unique platform for modern
materials design. JARVIS ensures openness of data and tools to enhance
reproducibility and transparency and to promote a healthy and collaborative
scientific environment
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