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Tardigrade (Quarterly Report Q1 FY2022)
Tardigrade is an effort to create tunable thermal expansion materials for use in a ruggedized lens housing. This requires new computational algorithms to model and predict thermal performance of meta-materials composed of multiple structured base materials and void-space, along with matching and developing 3D print technology to demonstrate the housing. The project is 27 months into the 36-month plan. We are continuing effort on 3 main technical thrusts: material design algorithm development (transitioning into full 3D design), multi-material additive manufacturing process exploration, and sensor/optics design and engineering. In the last quarter, we have focused on developing the code for 3D Topology Optimization, building data sets for 2D autoencoder training, and finishing lens housing engineering for the microbolometer based test sensor. We are exploring 2 potential multi-material AM technologies, a polymer-based technique in development at LLNL and a metal SLS system produced by Aconity, called the AeroSint deposition head.
Algorithmic and GPU enhancements for molecular dynamics in Cabana and LAMMPS
The focus of this milestone was to implement and test new algorithms and optimizations for improved GPU performance by molecular dynamics (MD) and related particle codes. The work was done in the CoPA Cabana library, the CabanaMD mini-app which uses Cabana to implement and benchmark prototypical MD models, and the LAMMPS MD code which is used by the ECP EXAALT project as well as for materials modeling generally. Efforts included (a) implementation of new or optimized algorithms for fundamental MD kernels like neighbor-list building and FFTs which are also widely used in other particle methods, (b) performance testing of data structure layouts for both simple pairwise and computationally intense neural network potentials, (c) optimizations aimed at improving GPU performance for models with small atom counts, and (d) optimizations specific to the SNAP interatomic potential due to its importance for the EXAALT project.
Exceptional Points in Novel Multiscale Quantum-Nanoplasmonic Materials for Enhanced Sensing and Other Applications
Lossy quantum systems can display fascinating behaviors around singularities known as exceptional points in their complex eigenvalue spaces. Interest in these systems was ignited over two decades ago when Carl Bender and Stefan Boettcher—a LANL Director’s Postdoctoral Fellow at the time—pointed out that many features of conventional lossless quantum systems, such as real operator eigenvalues, could be recovered in lossy systems exhibiting parity- and time-reversal (ΡΤ) symmetry.
Non-equilibrium phases in circularly confined active nematics [Slides]
Abstract not provided.
Surface Area of Lignocellulosic Material using Physisorption [Slides]
Abstract not provided.
Computational Design of Stable Acid Coordinated Quaternary Ammonium Polymers for High Temperature Fuel Cells [Slides]
We reported a protonated phosphonated ionomer that increases proton conductivity in high-temperature polymer electrolyte membrane fuel cells for more than an order of magnitude as compared with a non-protonated phosphonated ionomer and enables remarkable power density well suited for heavy-duty vehicles.
Exploring strongly correlated quantum spin systems with quantum computers
At inception, quantum annealing leveraged quantum mechanics for classical optimization tasks. However, as machine coherence increases, the realization of quantum spin systems has emerged as an even more fruitful application of this computational model. Alternatives to the standard gate model deserve exploration, to achieve useful quantum advantage via analog quantum computing. The recent demonstration of so-called coherent quantum annealing with 1,000s of qubits, further expands the potential for this hardware to explore quantum system dynamics where the effects of quantum fluctuations can be carefully controlled and observed directly. Implementing existing celebrated spin models—or in fact new and dedicated ones—into quantum annealers will lead to observation and detection of quantum phenomena not yet observed, or not visualized directly, in experimental physics laboratories. Rather than computing or simulating quantum systems, these quantum computers allow one to simply build quantum systems, and experiment on them in an uniquely controlled way, with characterization down to the constitutive degree of freedom. This provides an unprecedented opportunity for understanding the physics of quantum spin systems. Keywords: Theoretical physics currently abounds of interesting theoretical spin models to explore frustration, strongly correlated spins, spin liquids, fractionalized excitations, and topological matter. However enticing, such models are generally only weak proxies for the properties of actual materials. In quantum annealers these models could be realized and experimented upon. Moreover, many more realistic models of such materials could be realized in quantum annealers. Employed in this way, quantum annealers provide an extraordinary versatile platform to explore quantum effects that are hard to find, detect, and characterize in natural materials.
Using Magnetic Proximity Effects to Build Designer Quantum Materials [Slides]
The properties of naturally occurring materials are not necessarily commensurate with those needed for next-generation devices. Counter to conventional thought, we find magnetic proximity effects can be asymmetric. In fact, our experimental data and DFT calculations indicate this effect is universal, with material and heterostructure specificity being vital for predictive modeling. This work suggests routes towards rational design of device component materials via selective control over spin valley states.
How to Make a Lightbulb That Is a Million Times Smaller Than an Ant [Slides]
Abstract not provided.
Near Infrared Plasmonic Properties in Spinel Metal Oxide Nanocrystals [Poster]
Spinel iron oxide nanocrystals are shown to support NIR LSPR. LSPR is dependent on size and Fe 2+ : Fe 3+ ratio and can be tuned to cover telecommunications region via various synthetic controls. Coupling IR emitting QDs with Fe 3 O 4 nanocrystals exhibiting overlapping plasmonic behavior resulted in faster emission. Plasmonic nanocavity optimizes the Purcell effect. Future work aims to integrate Fe 3 O 4 nanocubes into nanogap antenna construction.
The Hunt for High-Tc Superconductivity: from Discovery to Breakthrough [Slides]
Summary/Outlook: BCS pairing theory of superconductivity is a prototypical example of a condensed matter physics problem. It has inspired the Weinberg Salam model for Electroweak interactions; So far there is no quantitative theory of superconductivity in strongly correlated materials. The limits on Tc are still unknown; Almost all known superconducting materials were found without theoretical guidance; The next-generation of first-principles approaches is beginning to captures a more holistic picture of correlated materials, giving way to a more quantitative theory of materials.
IMS Rapid Response 2023-2 (RR 2023-RND-2): Magnetic order in layered bismuthide RhMnBi 3 (Final Report)
Microelectronics are technologies (mostly theoretical at this point) to create electronic circuits with components of atomic length scale. One of the key materials innovations enabling this technology is exfoliatable two-dimensional materials. These materials allow thin sheets of only a few atoms thick to be easily created in the laboratory. More and more of these materials are reported every year, but few have been characterized in detail. Thus a major goal in materials research in pursuit of microelectronic devices is characterizing newly discovered materials to evaluate their properties. The goal of this project was the measure and understand the magnetic order in a newly discovered van der Waals magnet RhMnBi 3 . Bulk property experiments indicated very complicated magnetic behavior, with multiple phase transitions between 2K and 300K (room temperature). This potentially indicated highly sensitive and tunable magnetism appropriate for single-layer magnetic switches and sensors.
Magnetic order in layered bismuthide RhMnBi 3 (Final Report) [Slides]
Abstract not provided.
Generalized spin dynamics and anisotropy renormalization [Slides]
Abstract not provided.
Unravel Electronic Structure in Strongly Correlated Materials [Slides]
Outline: Introduction and motivation - Correlated electron materials; Theoretical approaches to strongly correlated materials - First-principles dynamical mean-field theory (DMFT) framework - Applications to f -electron correlation effects; Summary and outlook.