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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Non-local corrections to the typical medium theory of Anderson localization
We use the recently developed finite cluster typical medium approach to study the Anderson localization transition in three dimensions. Applying our method to the box and binary alloy disorder distributions, we find a fast convergence with the cluster size. We demonstrate the importance of the typical medium environment and the non-local spatial correlations for the proper characterization of the localization transition. As the cluster size increases, our typical medium cluster method recovers the correct critical disorder strength for the transition. Our findings highlight the importance of the non-local cluster corrections for capturing the localization behavior of the mobility edge trajectories. Our results demonstrate that the typical medium cluster approach developed here provides a consistent and systematic description of the Anderson localization transition in the framework of the effective medium embedding schemes.
Towards increasing the performance of FTICR-MS with signal detection at frequency multiples: Signal theory and numerical study
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Modeling water diffusion in polybenzimidazole membranes using partial immobilization and free volume theory
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Substituted ALPO-5 Zeolites as Promising O 2 Sorption Pump Materials: A Density Functional Theory Study
Many chemical processes depend on having an environment that is low in oxygen partial pressure (P O2 < 100 Pa); sorption pumps are a promising route to establishing that environment by either oxygen pumping or oxygen separation from an inert gas. Near ambient sorption-based processes rely on either pressure or thermal swings, requiring no moving parts, no electricity, and neither very high nor very low temperatures. In this work, we use ab initio calculations to explore zeolites as a class of materials for sorption based oxygen pumping/separation. Our calculations indicate that while the neat ALPO-5 zeolite does not adsorb O 2 , O 2 does adsorb on zeolites selectively substituted with transition metals and metalloids and hence, can enable separation and pumping. ALPO-5 substituted with Si, Ge, Sn, Pd, Pt, Ti, V, Cr, Mn, Zr, Mo, Hf, W, Ce, and Pr provides adsorption energies ranging from -0.19 to -3.92 eV, (-) indicates exothermic process. Additionally, we provide a comprehensive understanding of what controls the adsorption energy: 1) the substi-tutions must be able to adopt an oxidation state that is more positive than the cation it replaces, and 2) the size of the pore into which the O 2 adsorbs to the wall. Additionally, we conduct a ther-modynamic analysis of a thermal swing cycle to approximate the optimal O 2 binding energy for 2 low energy O 2 pumping/separation. We find that the minimum energy cost likely occurs when the adsorption energy is in the range of 0.75 – 1.00 eV (72 – 97 kJ·mol -1 ), which corresponds to Ge, V, Pt, or Ce substituted ALPO-5.
Theory-Enabled High-Throughput Screening of Ion Dissociation Explains Conductivity Enhancements in Diluted Ionic Liquid Mixtures
The growing demand for room-temperature ionic liquids (RTILs) for energy applications necessitates the development of an efficient screening platform. Here, in this study, we successfully developed a fully automated high-throughput RTIL screening platform specifically designed for assessing ionic conductivity. By utilizing the 96 wells of a microtiter plate as individual electrolysis cells, we measured the ionic conductivity of 22 different RTILs, encompassing various combinations of cations and anions, and benchmarked the values with existing literature. We also employed the screening platform to investigate the conductivities of RTIL mixtures with a nonaqueous solvent, ethylene glycol (EG). Specific combinations of RTILs with EG result in approximately 200% enhancement in the conductivity values compared to the pure RTILs. To understand the underlying mechanisms responsible for this enhancement, we developed a theoretical framework for ionic conductivity that considers factors such as the degree of dissociation, viscous forces, and molal volume of the RTIL-EG mixtures. The optimized electrolyte mixture was then employed in the migration-assisted moisture gradient (MAMG) CO 2 capture process to study the effects of improved ionic conductivity on the energy efficiency of the process. Notably, the enhanced conductivity of the RTIL-EG mixture led to a nearly 50% reduction in energy consumption for capturing CO 2 . These outcomes highlight the effectiveness of our strategy in screening RTILs and improving existing processes. Moreover, this fully automated high-throughput setup, combined with the developed theoretical framework, provides a comprehensive platform for screening and studying RTIL mixtures with different solvents, enabling their application in various fields.
Scrutinizing formally Ni IV centers through the lenses of core spectroscopy, molecular orbital theory, and valence bond theory
Nickel K- and L 2,3 -edge X-ray absorption spectra (XAS) are discussed for 16 complexes and complex ions with nickel centers spanning a range of formal oxidation states from II to IV. K-edge XAS alone is shown to be an ambiguous metric of physical oxidation state for these Ni complexes. Meanwhile, L 2,3 -edge XAS reveals that the physical d-counts of the formally Ni IV compounds measured lie well above the d 6 count implied by the oxidation state formalism. The generality of this phenomenon is explored computationally by scrutinizing 8 additional complexes. The extreme case of NiF 6 2- is considered using high-level molecular orbital approaches as well as advanced valence bond methods. The emergent electronic structure picture reveals that even highly electronegative F-donors are incapable of supporting a physical d 6 Ni IV center. The reactivity of Ni IV complexes is then discussed, highlighting the dominant role of the ligands in this chemistry over that of the metal centers.
Theory of cross phenomena and their coefficients beyond Onsager theorem
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The Case for an EIC Theory Alliance
This documents outlines the case for the creation of an EIC Theory Alliance. The EIC will be a unique and versatile facility that will enable the understanding of some of the most compelling questions in the physics of the strong nuclear force. To fully exploit the potential of the EIC, a focused theory effort will be required. The goal of the EIC Theory Alliance is to provide support and stewardship of the theory effort in EIC physics, broadly defined, over the lifetime of the facility. It will promote EIC theory and contribute to workforce development through: support of graduate students; EIC Theory Fellowships for postdocs; bridge positions at universities; and short and long term visitor programs to enhance collaboration between groups. In addition, the alliance will organize topical schools and workshops. The EIC Theory Alliance will be a decentralized organization, open to participation by anyone in the community who is interested in EIC physics, i.e., it will be a membership organization, where members elect an executive board which will effectively run the alliance. The executive board will determine the major scientific thrusts of the theory alliance, make decisions regarding at which universities bridge faculty positions will be created, and serve as a search committee for EIC-related positions. Furthermore, the executive board will coordinate the organization of workshops and schools related to the research activities of the alliance. In addition, the EIC theory alliance will seek out and nurture international cooperation to maximally leverage the available funding. The EIC theory alliance has a wider range of physics goals and longer lifetime, commensurate with that of the EIC research program, than individual nuclear theory topical collaborations. The structure of the EIC Theory Alliance will build on previous examples of successful alliances in nuclear theory.
Dissertation Proposal: Innovations in Pulsed Power and Plasma Science Theory Simulation and Experiment
Pulsed power and plasma physics are topics of great study at both Sandia National Laboratories (SNL or Sandia) and the University of New Mexico (UNM). The goal of this research is to further knowledge and understanding of these fields using the resources of both SNL and UNM in three ways. The first way is through the comprehension, application, and testing of theory. Reading and analytically deriving theoretical solutions of problems both real-world and simplified will allow for a fresh perspective and the furthering of the theory. One such theory is Ottinger's generalized theory for voltage measurement in magnetically insulated transmission lines (MITLs). By working through the math, a deeper understanding of the theory is gained from which one may add more physically accurate and/or more detailed physics into the theory. Additionally, understanding the theory lays a good foundation from which one can analyze, test, and compare results to the theory in the following two ways that will advance the fields of pulsed power and plasma physics. The second way is through the modeling and simulation of real-world and simplified problems that utilize and test the afore mentioned theories. Theory can be applied to a simulation domain by using the unstructured time-domain electromagnetic (UTDEM) codes EMPHASIS and EMPIRE as well as the physical modeling software CUBIT, all of which were developed at SNL. Problems such as the modeling and design of the extended MITL on HERMES III, the understanding of space-charge-limited emission from vacuum cathodes, and the interaction between a relativistic electron beam and an ideal gas can all be modeled, simulated, and analyzed with this set of codes. Here the advantage is three-fold. Firstly, theory that describes our understanding of these problems can be put to the test and advanced through iterative simulation and analysis. Secondly, the understanding of these problems will have a positive impact on national security through the advancement of the technological capability of the United States of America. Thirdly, and not unrelated to the prior advantage, is the validation and verification of EMPIRE and EMPHASIS. This segues into the third way, which is through experiment and the comparison of experiment to simulated and theoretical results. Performing experimental comparisons completes the scientific method and grounds all of the work in reality. Being able to physically test theory and simulation is necessary for any real conclusions to be drawn. Another advantage for carrying out experimental work is to advance the physical testing capabilities of SNL. Several systems will be developed and tested through the course of this work that positively impact technological advancement of Sandia National Labs. Lastly, all of the above work will converge to yield a well-rounded perspective that ties the three categories of research together.
New Theories for Neutrino Masses and Dark Matter
The main goal of the project is to investigate new theories for neutrino masses and dark matter, and understand their testability in different experiments. The PI proposed several mechanisms for neutrino masses in the context of B-L theories, left-right symmetric theories, supersymmetric theories and grand unified theories. The PI would like to investigate new ways to understand the origin of neutrino masses where the seesaw scale is in the multi-TeV region. One can have a multi-TeV seesaw scale in scenarios where the same symmetry relevant for neutrino masses defines the dark matter relic density, or in the minimal supersymmetric theory based on local B-L. In these theories one can have new ways to understand the testability of the origin of neutrino masses at colliders and low energy experiments. In these theories one predicts the possibility to observe lepton number violating signatures at the LHC, one can predict large contributions to lepton number violating processes such as mu to e conversion, neutrinoless double beta decay experiments and others. The nature of the dark matter in the Universe is one of the most important problems in cosmology. Two of the most popular candidates are the Axions and the Weakly Interacting Massive Particles (WIMPs). The PI would like to investigate the implications of a new electroweak theta term similar to the QCD vacuum angle but in the SU(2) gauge sector of the SM which is physical if the baryon and lepton numbers are broken symmetries. We will investigate the implications of having a new electroweak theta term dark matter portal, the implications for baryogenesis and understand the constraints coming from different experiments such as the searches for electric dipole moments and axion experiments. The implications of having the electroweak theta term in theories with different sources of baryon and lepton number violation will be investigated. WIMPs are perhaps the most appealing candidates for many reasons. The PI would like to investigate the properties of WIMPs in different gauge theories, study the implications of the cosmological bounds on the WIMPs relic density for the symmetry breaking scale in models for new physics. The PI would like to investigate in great detail the predictions for gamma lines, neutrino lines and other striking signatures which can be present in these theories. These studies can have a profound impact in the testability of different theories for physics beyond the Standard Model.
Entanglement in Gravity and Quantum Field Theory (Final Report)
It is becoming increasingly clear that ideas from quantum information theory, particularly the notion of quantum entanglement, play a fundamental role in some of the deepest aspects of our modern theories of quantum fields and gravity. The aim of this research was to explore the role that quantum entanglement plays in quantum field theories and in the nature of space-time and gravity. Building on a variety of earlier results obtained in these regards at the University of Illinois, we explored the constraints on the dynamical content of quantum field theories that follow from their entanglement properties. Topological field theories are important examples of particularly simple quantum field theories whose patterns of entanglement make connections between high energy physics, condensed matter physics and mathematics. These theories are directly relevant to low energy properties of certain materials. The study of such theories allowed us to investigate ideas that are relevant to quantum information research, such as new notions of entanglement between multiple parties and the quantum properties of interfaces between different phases of such materials. In addition, we employed new results in mathematics which strengthen monotonicity constraints on relative entropy to study their ramifications in quantum field theories, and we used quantum information methods to study the emergence of quantum gravity and string theory in holographic quantum field theories.
Core excitations with excited state mean field and perturbation theory
In this work, we test the efficacy of excited state mean field theory and its excited-state-specific perturbation theory on the prediction of K-edge positions and x-ray peak separations. We find that the mean field theory is surprisingly accurate, even though it contains no accounting of differential electron correlation effects. In the perturbation theory, we test multiple core-valence separation schemes and find that, with the mean field theory already so accurate, electron-counting biases in one popular separation scheme become a dominant error when predicting K-edges. Happily, these appear to be relatively easy to correct for, leading to a perturbation theory for K-edge positions that is lower scaling and more accurate than coupled cluster theory and competitive in accuracy with recent high-accuracy results from restricted open-shell Kohn-Sham theory. For peak separations, our preliminary data show excited state mean field theory to be exceptionally accurate, but more extensive testing will be needed to see how it and its perturbation theory compare to coupled cluster peak separations more broadly.