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Transfer Learning Meets Embedded Correlated Wavefunction Theory for Chemically Accurate Molecular Simulations: Application to Calcium Carbonate Ion Pairing
Achieving chemical accuracy for molecular simulations remains a central challenge in computational chemistry. Here, we present an embedded correlated wavefunction transfer learning (ECW-TL) framework for accurately simulating molecular dynamics in the condensed phase. ECW-TL incorporates high-level electron exchange and correlation effects in ECW theory while preserving the training and computational efficiency of machine-learned interatomic potentials. We demonstrate the framework on Ca 2+ –CO 3 2– ion pairing in aqueous solution, a key process underlying CO 2 mineralization in seawater. As proof of principle, we first show that fine-tuning a DFT-revPBE-D3(BJ) baseline model with embedded-DFT-SCAN data reproduces the DFT-SCAN free-energy surface within 1 kcal/mol across all solvation states. Extending the framework to embedded MP2 and localized natural-orbital CCSD(T) further refines the free-energy profile, revealing the crucial role of exact electron exchange and correlation in determining ion-pair stability and structure. The computed ion-pair association free energy is in quantitative agreement with experimental measurements, further validating the accuracy of the ECW-TL framework. ECW-TL thus provides a general, data-efficient route for transferring CW accuracy to efficient simulations of complex aqueous and interfacial chemical processes.
Charge Transport Properties of Lithium Superoxide in Li–O 2 Batteries
The theoretical energy density of lithium–oxygen (Li–O 2 ) batteries is extremely high, although there are many challenges that must be overcome to achieve high energy density in a manufactured cell. For example, little is known about the properties of one of the key intermediates, lithium superoxide (LiO 2 ), which until recently had not been stabilized in bulk form. In this work, lithium superoxide was deposited onto iridium–reduced graphene oxide (Ir–rGO) cathodes in a Li–O 2 system under a flow of O 2 . Lithium peroxide (Li 2 O 2 ) was subsequently produced on the cathode surface in an inert Ar atmosphere. Based on a detailed analysis of electrochemical impedance spectroscopy data, it was demonstrated experimentally for the first time that the charge transport resistance through LiO 2 was much lower than for Li 2 O 2 and correlated with lower LiO 2 charge overpotentials. We report this result indicates that LiO 2 has good electronic conductivity and confirms previous theoretical predictions that bulk LiO 2 has better charge transport properties than Li 2 O 2 . In addition, impedance and other characterization of Li 2 O 2 formation from LiO 2 in an Ar atmosphere revealed that when surface-mediated Li 2 O 2 formation occurs, it has a significantly lower discharge potential than when it forms through a solution-phase-mediated process. These significant findings will contribute to the development of Li–O 2 batteries through better understanding of LiO 2 properties and formation mechanisms.
Assembly of Disordered Cocontinuous Morphologies by Multiblock Copolymers with Random Block Sequence and Length Dispersity
Among the wide variety of nanostructures accessible by self-assembly of block copolymers, cocontinuous morphologies are of great interest for separations, catalysis, sensing, and energy storage due to their ability to integrate distinct properties of the constituent polymers. Furthermore, we investigate the tendency to form disordered cocontinuous phases of multiblock copolymers (MBCs) with random block sequence and length dispersity prepared by step-growth polymerization of pre-made telechelic polymers, specifically using thiol-Michael addition between diacrylate functionalized polystyrene (PS) and poly (D,L - lactide) (PLA) chains and a small molecule dithiol. In the phase diagram so established, disordered cocontinuous nanostructures occupy a wide window (≈ 25 % vol) at a modest segregation strength of χN = 15, close to the critical value for microphase separation. At a higher segregation strength of χN = 30, only a moderately wide (≈ 10 vol %) cocontinuous window is found, with MBCs instead tending to form ordered nanostructures. Although the breadth of the cocontinuous widow is less than that found in prior work on analogous randomly end-linked copolymer networks (RECNs), the MBC architecture offers offsetting advantages in terms of solution and melt processability.
An eigenvalue-based method for computing the relaxed pressure in compressible multiphase flow with N phases
The modeling of compressible multiphase flows is a decades-old area of study with many applications across various fields. Many of these application areas use stiff pressure relaxation. This process involves the solution of a nonlinear system with N + 1 equations and N + 1 unknowns, where N is the number of phases. The resolution of this system with general equations of state (EOSs) is difficult. Furthermore, nonlinear systems can admit multiple solutions, and current solution methods do not address this possibility. Very recently, a thermodynamic relaxation method was introduced, which effectively maps a relatively simple predictor equation of state onto a more complex target equation of state. In this context, the target EOSs are the chosen EOSs for the thermodynamic model. Furthermore, this thermodynamic relaxation has the benefit of simplifying the stiff pressure relaxation system of equations. In this article, we show this system reduces to a polynomial of degree N, which can be recast as an eigenvalue problem through the use of the associated companion matrix. We show that although this eigenvalue method is generally less efficient than Newton–Raphson iteration, it does not suffer from convergence issues and finds all N roots of the polynomial. Hence, the method provides a fail-safe for root-finding iterative methods and a way to address the issue of multiple solutions to the nonlinear system of equations in stiff pressure relaxation.
Recent advances of two-dimensional material additives in hybrid perovskite solar cells
Perovskite solar cells (PSCs) have become one of the state-of-the-art photovoltaic technologies due to their facile solution-based fabrication processes combined with extremely high photovoltaic performance originating from excellent optoelectronic properties such as strong light absorption, high charge mobility, long free charge carrier diffusion length, and tunable direct bandgap. However, the poor intrinsic stability of hybrid perovskites under environmental stresses including light, heat, and moisture, which is often associated with high defect density in the perovskite, has limited the large-scale commercialization and deployment of PSCs. The use of process additives, which can be included in various subcomponent layers in the PSC, has been identified as one of the effective approaches that can address these issues and improve the photovoltaic performance. Among various additives that have been explored, two-dimensional (2D) materials have emerged recently due to their unique structures and properties that can enhance the photovoltaic performance and device stability by improving perovskite crystallization, defect passivation, and charge transport. In this work, we provide a review of the recent progresses in 2D material additives for improving the PSC performance based on key representative 2D material systems, including graphene and its derivatives, transitional metal dichalcogenides, and black phosphorous, providing a useful guideline for further exploiting unique nanomaterial additives for more efficient and stable PSCs in the near future.
Water dynamics in pristine and porous Ti 3 C 2 T x MXene as probed by quasielastic neutron scattering
MXenes are a novel class of two-dimensional (2D) materials whose applications in energy-storage systems have attracted substantial attention. Still, the rate performance of these materials is often diminished by sheet restacking, which is attenuated via controlled etching in H 2 SO 4 solution. With this process, micropores are formed in MXene sheets that allow transport across 2D layers. As a result, the intercalation and diffusivity of ions are facilitated resulting in improved capacitance retention at high charge-discharge rates. In the present work, we used quasielastic neutron scattering to evaluate the potential changes in water dynamics as a consequence of this mechanism by assessing the behavior of weakly and strongly confined water populations in pristine and porous MXenes. First, we have found that the porous sample accommodates a noticeably higher content of both water populations. Additionally, the fraction of mobile molecules is higher either under strong or weak confinement. Interestingly, regardless of the abundance of weakly confined water in the porous sample, no considerable changes in the dynamical behavior were detected in comparison with the dynamics measured in the pristine material. Finally, for the strongly confined populations of water, our results show that water is able to permeate the micropores introduced by etching and perform unlocalized motions.
Isolating Insecurely: A Call to Arms for the Security and Privacy Community During the Time of COVID-19
The privacy question is one that has only begun to be addressed. While on one hand, many of the staunchest privacy advocates have argued for relaxation of privacy controls in order to develop better tests, “back to work” protocols, and vaccines and other treatments, the same advocates point out that any loss of privacy for the public good should be temporary, transparent, necessary, proportionate, and follow a due process. What should solutions look like for data gathering, sharing, use, and disposal; or for protocols requiring strong individual identity verification and validation?
Group-V Doping Impact on Cd-Rich CdTe Single Crystals Grown by Traveling-Heater Method
Cd-rich CdTe single crystals were grown from Cd solvent in the traveling-heater method (THM) rather than the more common Te solvent used for high-resistivity CdTe. The growth process from Cd solution in terms of the solid-liquid interface shape and group-V doping under Cd-rich condition were investigated. Stable, flat solid-liquid interfaces can be obtained by optimizing THM furnace temperature profile. An apparent doping limit in the 10^16 to 10^17 cm^ -3 range which scales weakly with increasing group-V element concentrations in the Cd-rich CdTe samples were indicated from capacitance-voltage measurement. The two-photon excitation time-resolved photoluminescence revealed a bulk lifetime of 20-40 ns.
Synthesis and Molecular Structures of (3-Hydroxy, 3-Chloro, 3-Arylamino)-N-acetyl-3-arylaminotropones
The structures of 5,7-di(tert-butyl)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)-3-hydroxytropone, 5,7-di(tert-butyl)-3-chloro-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)tropone, 5,7-di(tert-butyl)- 3-(3,5-dimethylphenylamino)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)tropone, and 3-(N-acetyl-3,5- dimethylphenylamino)-5,7-di(tert-butyl)-2-(5,8-dimethyl-4-piperidinoquinolin-2-yl)tropone were determined by X-ray diffraction. These compounds were synthesized through a series of transformations, including the nucleophilic substitution of the chlorine atom by piperidine in the starting 5,7-di(tert-butyl)-2-(4- chloroquinolin-2-yl)-3-hydroxytropone followed by the three-step functionalization of the 3-position in 3-hydroxytropone. The nature of dynamic processes in a solution of N-acetyl-3-arylaminotropone associated with the rotation of the N-acetyl group was revealed by the PCM/PBE0/6-31G(d,p) method.
Solvent Hold Tank Sample Results for MCU-18-123- 125 (April 2018), MCU-18-135-137 (May 2018), and MCU-18-192-197(June 2018): Quarterly Report
A trend summary of three Solvent Hold Tank (SHT) monthly samples MCU-18-123-125, MCU-18-135- 137, and MCU-18-192-197 are reported. Most of the conclusions are based on the June SHT sample (MCU- 18-192-197). Analyses of the June SHT sample (MCU-18-192-197) indicated that the Modifier (CS-7SB) and the extractant (MaxCalix) concentrations were at the nominal recommended concentrations (169,000 mg/L and 46,400 mg/L respectively). The suppressor ( N,N’,N” –tris(3,7-dimethyloctyl)guanidine or TiDG) concentration has decreased since the April 2018 measurement (Modular Caustic-Side Solvent Extraction Unit or MCU resumed processing radioactive salt solution from May through August 2018) to 1,116 mg/L, well above the minimum recommended concentration (479 mg/L), but below the nominal concentration. The apparent “downwards” trends observed in the TiDG, MaxCalix, Modifier, and gamma measurement are consistent with the start up (and/or proficiency runs) of MCU on May 22, 2018 since these new concentrations are consistent with the concentrations observed when MCU was fully operational in 2016.
Report on the FY18 creep rupture and creep-fatigue tests on the first commercial heat of Alloy 709
Creep, fatigue and creep-fatigue tests were performed on the Carlson plate of Alloy 709 (ID 58776). The plate, which is the first of the commercial heats tested, was divided into several sections, each undergoing different processing conditions. The effects of processing method and solution annealing temperature were studied in FY18 to inform best procedures for the second heat. The solution annealing temperature of 1050°C was found to be unacceptable due to the grain size being smaller than allowed by the specifications, as well as generally having poor creep properties. Both argon oxygen decarburization AOD and electro-slag remeltin ESR were found to have desirable properties, and the homogenization heat treatment was found to not significantly improve the mechanical properties.
Solvent Hold Tank Sample Results for MCU-18-301- 303 (July 2018), MCU-18-357-359-360 (August 2018), and MCU-18-402-410 (September 2018) (Quarterly Report)
A trend summary of three Solvent Hold Tank (SHT) monthly samples; MCU-18-301-302-303, MCU-18- 357-359-360 and MCU-18-402-410 are reported. Most of the conclusions are based on the September SHT sample (MCU-18-402-410). Analyses of the September SHT sample (MCU-18-402-410) indicated that the Modifier (Cs-7SB) and the extractant (MaxCalix) concentrations were below their nominal recommended concentrations (169,000 mg/L and 46,400 mg/L respectively) by 5% and 8% respectively. The suppressor (N,N’,N”–tris(3,7-dimethyloctyl)guanidine or TiDG) concentration has decreased since the April 2018 measurement (Modular Caustic-Side Solvent Extraction Unit or MCU resumed processing radioactive salt solution from May through August 2018) to 241 mg/L, well below the minimum recommended concentration (479 mg/L). The apparent “downwards” trends observed in the TiDG, MaxCalix, and Modifier measurements are consistent with the startup (or Proficiency Runs) of MCU on May 22, 2018; new levels are consistent with the concentrations observed when MCU was fully operational in 2016. This analysis confirms the Isopar™ L addition to the solvent on July 2 and August 9, 2018. This analysis also indicates the solvent did require a trim addition. Based on the current monthly sample, the concentrations of Isopar™ L, MaxCalix, and Modifier are sufficient for continuing operation but are expected to decrease with time. The TiDG concentration was below its recommended level. Periodic characterization and trimming additions to the solvent are recommended. The Semi-Volatile Organic Analysis (SVOA) did not detect any impurities. However, the Fourier Transform Hydrogen Nuclear Magnetic Resonance (FT-HNMR) analysis detected a low concentration of sec-butyl phenol (SBP) at levels of a few ppm. The impurity concentration was highest in the July sample and consistently detected in the August and September samples (but always a few ppm or less). The source of this impurity is due to the degradation of the Modifier. Another impurity observed in the samples was mercury. Based on the September SHT sample, up to 17 ± 3 micrograms of mercury per mL of solvent was detected (the average of the Direct Mercury Analysis (DMA) and X-Ray Fluorescence (XRF) methods). The higher mercury concentration in the solvent (as determined in the last three monthly samples) is possibly due to the higher mercury concentration in Salt Batches 9 and 10 (SB 10 was recently added to Tank 49H in March 2017). The gamma concentration (~2.3E5 dpm/mL) measured in the September SHT samples was consistent with previous values observed when MCU was fully operational (for example, between December 2016 and January 2017) and it was lower than the April SHT measurement. The “dip” in the gamma measurement for the May 2018 SHT sample was due to Isopar™ L addition to MCU during April and May 2018. The laboratory will continue to monitor the quality of the solvent for any new impurities or degradation of the solvent components.
Cesium Removal Performance Comparisons of Crystalline Silicotitanate Media Batches with Savannah River Site Waste Simulant
The Tank Closure Cesium Removal (TCCR) system uses ion exchange columns filled with Crystalline Silicotitanate (CST) media to process radioactive waste solutions for the removal of Cs- 137. The TCCR project is currently focused on dissolving Savannah River Site (SRS) Tank 10H waste (primarily sodium salt cake solids) within the tank followed by at-tank ion exchange column treatment. Plans are underway to prepare and install a second TCCR unit at SRS. Capacity and particle size differences exist between archived (IE-911) and more recently prepared CST media batches (9120-B and 9140-B). Side-by-side comparison testing was performed to evaluate the cesium removal performance of each batch to aid in selecting the preferred CST batch and media characteristics to load into the second TCCR unit. Batch contact equilibrium and flow-through column tests have been conducted with three CST batches using an SRS Average Simulant.
High Temperature Thermal Barrier Coating Evaluation of Yttrium Aluminum Garnet for Gas Turbine Applications
The Solution Precursor Spray Process (SPPS) process has been shown to overcome the durability and property challenges of applying yttrium aluminum garnet (YAG) coating for high temperature thermal barrier coating (TBC) applications (1200°C+) but only limited testing has been performed in representative application environments. In this study, YAG coatings were developed to optimize microstructure and tailor properties for combustion components in an industrial gas turbine. Thermal conductivity, erosion resistance and furnace cycling durability were used to validate YAG properties against the standard yttria-stabilized zirconia coating (YSZ). Graded and multi-layered microstructures were applied to enhance performance while maintaining durability. Further YAG process development was required to replicate coating properties and optimize deposition on more complex fuel injector nozzle and combustion liner components. Rig testing of both components was performed and compared against the baseline YSZ coating validating the high temperature capability and lower thermal conductivity of the SPPS YAG coating. The components in both tests were cycled for a minimum of ten cycles with the fuel injector test targeting a higher operating temperature while the combustor liner operated at standard conditions. A development engine test is planned to further validate performance in a gas turbine engine of this promising material.
LANL’s Digital Supply Chain Transformation with Ariba Part 2 [Slides]
LANL’s budget continues to increase. Our annual procurement spend has increased from approximately 750 million two years ago to 1.4 Billion in FY21. Procurement for LANL is a mix of indirect and direct but had limited managed spend – more standalone orders vs master contracts. The level of transformation we were looking to achieve required a comprehensive approach, encompassing people, processes and software solutions.
Microgrid Conceptual Design Guidebook | 2022
This guide is meant to assist communities – from residents to energy experts to decision makers – in developing a conceptual microgrid design that meets site-specific energy resilience goals. Using the framework described in this guidebook, stakeholders can come together and start to quantify site-specific vulnerabilities, identify the most significant risks to delivery of electricity, and establish electric outage tolerances across the community. In addition to establishing minimum service needs, this framework encourages communities to consider broader sustainability goals and policy constraints and begin to estimate up-front costs associated with the installation of alternative microgrid solutions. The framework guides a community through data collection and a high-level assessment of its needs, constraints, and priorities, prior to engaging engineers, vendors, and contractors. The first sections of this guidebook provide a high-level primer on electric systems. The latter sections include guidance for step-by-step data gathering and analysis of site conditions. The ultimate product resulting from the stepwise approach is a conceptual microgrid design. A conceptual design is defined as an initial design (10%-20% complete) that considers the specific threats, needs, limitations, and investment options for a given location. Going through this exercise and developing the conceptual microgrid design as a community ensures the same community members who will ultimately live with the solution are the developers of its foundational design. Often, these are also the very same people who understand system tolerances and needs the best and are therefore the ideal candidates for establishing these criteria. Especially when it comes to evaluating critical infrastructure, it is the community that best understands the most critical services. The framework is intended to facilitate a systematic approach to planning for resilience and provide a deeper understanding of how to use a framework to make decisions around microgrid solutions. Like many processes where tradeoffs need to be considered, this is often an iterative process. If this guide serves to help educate and empower communities who are beginning the process of deploying a microgrid, it has met the goal of its authors.
Low-cost sensors and analytics for a digital factory
ORNL Manufacturing Demonstration Facility and Perisense worked on a low-cost solution for machining process monitoring to enable a digital factory. Enabling machine connectivity for digital factors is expensive for many small to medium manufacturers. The hypothesis for the research project is that a lowcost sensor suite, which can be retrofitted to a legacy machine tool or a new machine tool, can effectively provide real-time, in-situ sensing for manufacturing processes, which can enable improvements in process performance and efficiency. The Perisense sensor node was installed on the Haas TM1 machine with a current sensor and an accelerometer. Cutting tests were performed at different process parameters and sensor data was recorded. Results show a correlation of the current sensor to the spindle load. The accelerometer, mounted on the machine base, showed a correlation to the spindle speed as well as the spindle load. The sensor data can be used to monitor the machining process and provide insights on the machine spindle load utilization.