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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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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Stable Cycling with Intimate Contacts Enabled by Crystallinity–Controlled PTFE–Based Solvent–Free Cathodes in All–Solid–State Batteries

All-solid-state batteries (ASSBs) employing Li-metal anodes and inorganic solid electrolytes are attracting great attention due to high safety and energy density for next-generation energy storage devices. However, the volume change of cathode active materials can cause contact loss, resulting in charge carrier isolation, heterogeneous current distribution, and poor electrochemical properties in ASSBs. Here, a simple, yet effective, solvent-free electrode engineering approach with polytetrafluoroethylene (PTFE) as a binder for ASSBs is reported, enabling intimate contact and stable interfaces with the cathode. It is substantiated that the crystallinity of PTFE can be controlled depending on the heat history, and highly crystalline PTFE displays robust mechanical properties. High-nickel LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode prepared with crystalline PTFE show improved cycle and rate performances in ASSBs. In addition, it is revealed that the intimate contact between cathode particles with a stable cathode electrolyte layer is maintained during cycling by postmortem studies. Furthermore, this simple engineering method can be applied to prepare cathodes with a variety of active materials and solid electrolytes in ASSBs.

25 ENERGY STORAGE↗
DOE OSTI2021

Short- and medium-range orders in Al90Tb10 glass and their relation to the structures of competing crystalline phases

Molecular dynamics simulations using an interatomic potential developed by artificial neural network deep machine learning are performed to study the local structural order in Al90Tb10 metallic glass. We show that more than 80% of the Tb-centered clusters in Al90Tb10 glass have short-range order (SRO) with their 17 first coordination shell atoms stacked in a ‘3661’ or ‘15551’ sequence. Medium-range order (MRO) in Bergman-type packing extended out to the second and third coordination shells is also clearly observed. Analysis of the network formed by the ‘3661’ and ‘15551’ clusters show that ~82% of such SRO units share their faces or vertexes, while only ~6% of neighboring SRO pairs are interpenetrating. Such a network topology is consistent with the Bergman-type MRO around the Tb-centers. Moreover, crystal structure searches using genetic algorithm and the neural network interatomic potential reveal several low-energy metastable crystalline structures in the composition range close to Al 90 Tb 10 . Some of these crystalline structures have the ‘3661’ SRO while others have the ‘15551’ SRO. While the crystalline structures with the ‘3661’ SRO also exhibit the MRO very similar to that observed in the glass, the ones with the ‘15551’ SRO have very different atomic packing in the second and third shells around the Tb centers from that of the Bergman-type MRO observed in the glassy phase.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mesoporous MoO 2 thin films for high rate Li + storage: Effect of crystallinity and porous structure

MoO 2 has attracted much recent attention as a high capacity energy storage material. While much of the current work on MoO 2 has been focused on the high capacity four-electron reduction, this reaction is limited to slow charging process due to the large volume change and phase transitions involved. In this study we focus on one-electron insertion reactions and demonstrate that ordered mesoporous thin films of MoO 2 can show signatures of pseudocapacitive charge storage. Mesoporous MoO 2 (mp-MoO 2 ) thin films were treated at different temperatures between 350 and 700 °C to explore the role of crystallinity and nanoscale structure on charging dynamics. The porosity and pore size decreased while the crystallinity and grain size increased as the calcination temperature increased. Materials processed at 600 °C showed the best electrochemical performance due to an optimized combination of high crystallinity and small grain size. These materials could be charged and discharged in 24 s while still achieving a Li + storage capacity of 158 mAh/g. While such thin film systems do not constitute a practical energy storage device, the work here provides structural design parameters for the production of future bulk nanoporous materials.

25 ENERGY STORAGE↗
DOE OSTI2019

Formation of Crystalline Silica–Carbonate Biomorphs of Alkaline Earth Metals (Ca, Ba, Sr) from Ambient to Low Temperatures: Chemical Implications during the Primitive Earth’s Life

The Earth has undergone at least four great glaciations, during which the ice layers and the glaciers have expanded all over the planet, corresponding to significant drops in global temperatures that lasted millions of years. Since the Precambrian era, ice ages have occurred at intervals of several millions of years. It is considered that the impact on the biosphere was large, because life was on the brink of disappearing completely from the planet. During these glaciation periods, carbon was reassigned, with the subsequent formation of carbonates called cap carbonates, which present stromatolite-like activity. These findings prove that life was conserved even during the glacial period. Knowledge on life conservation during the glacial period through stromatolites that have endured until the present day, is of special relevance. In recent investigations, in vitro structures have been synthesized; these crystalline aggregates have been named biomorphs because they mirror the morphologies of primitive organisms called Precambrian cherts. These biomorphs have been synthesized at different temperatures (from room temperature to lower ones). Finally, the aim of the present work was to synthesize CaCO 3 , BaCO 3 , and SrCO 3 silica–carbonate biomorphs at three low temperatures (4 °C, -20 °C, and -70 °C). CaCO 3 biomorphs present almost the same morphology at all temperatures with a calcite crystalline structure, whereas BaCO 3 and SrCO 3 biomorphs present remarkably different morphologies depending on temperature with witherite and strontianite crystalline structure, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Microscopic Mechanisms of Superionic Na-ion Conductivity in Crystalline and Amorphous NaMOCl 4 (M = Nb, Ta) Solid Electrolytes

Sodium-ion solid electrolytes offer a sustainable route toward next-generation batteries, but few match the performance of their lithium counterparts. Halide-based NaMOCl 4 (M = Nb, Ta) has recently emerged as a promising analogue to LiMOCl 4 , yet its structure–transport relationships remain unclear due to poor crystallinity in experiments. Here, we combine density functional theory and machine-learned molecular dynamics to reveal that crystalline NaMOCl 4 exhibits negligible room-temperature conductivity with high activation barriers arising from vacancy-mediated diffusion below an order–disorder transition. Above this transition, rotational and translational motion of the [MO 2/2 Cl 4 – ] ∞ chains create new Na sites and enhances transport. In contrast, the amorphous phase inherently supports facile, three-dimensional Na diffusion through dynamic framework flexibility. These results show that ordered crystalline phases hinder ionic transport, while disorder – either thermally induced or structural – facilitates it, revising prior assumptions from the Li system and providing design principles for high-conductivity Na halide electrolytes.

Wei, Grace [University of California, Berkeley, CA↗
DOE OSTI2024

Hybrid Molecular Beam Epitaxy for Single-Crystalline Oxide Membranes with Binary Oxide Sacrificial Layers

The advancement in thin-film exfoliation for synthesizing oxide membranes has led to possibilities for creating artificially assembled heterostructures with structurally and chemically incompatible materials. The sacrificial layer method is a promising approach to exfoliate as-grown films from a compatible material system, allowing for their integration with dissimilar materials. Nonetheless, the conventional sacrificial layers often possess an intricate stoichiometry, thereby constraining their practicality and adaptability, particularly when considering techniques such as molecular beam epitaxy (MBE). This is where easy-to-grow binary alkaline-earth-metal oxides with a rock salt crystal structure are useful. These oxides, which include (Mg, Ca, Sr, Ba)O, can be used as a sacrificial layer covering a much broader range of lattice parameters compared to conventional sacrificial layers and are easily dissolvable in deionized water. In this study, we show the epitaxial growth of the single-crystalline perovskite SrTiO 3 (STO) on sacrificial layers consisting of crystalline SrO, BaO, and Ba 1–x Ca x O films, employing a hybrid MBE method. Our results highlight the rapid (≤5 min) dissolution of the sacrificial layer when immersed in deionized water, facilitating the fabrication of millimeter-sized STO membranes. Using high-resolution X-ray diffraction, atomic-force microscopy, scanning transmission electron microscopy, impedance spectroscopy, and scattering-type near-field optical microscopy (SNOM), we demonstrate single-crystalline STO membranes with bulk-like intrinsic dielectric properties. The employment of alkaline earth metal oxides as sacrificial layers is likely to simplify membrane synthesis, particularly with MBE, thus expanding the research and application possibilities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Ester-Linked Crystalline Covalent Organic Frameworks

Ester-linked, crystalline, porous covalent organic frameworks (COFs) have been synthesized and structurally characterized. Transesterification reactions between ditopic 2-pyridinyl aromatic carboxylates and tri- or tetratopic phenols gave the corresponding ester-linked COFs. They crystallize as 2D structures in kgm (COF-119) and hcb (COF-120, 121, 122) topologies with surface areas of up to 2092 m 2 /g. Notably, crystalline COF-122 comprises edges spanning over 10 phenylene units, an aspect that had only been achieved in metal-organic frameworks. Finally, this work expands the scope of reticular chemistry to include, for the first time, crystalline ester-linked COFs related to common polyesters.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Distance-Selected Topochemical Dehydro-Diels–Alder Reaction of 1,4-Diphenylbutadiyne toward Crystalline Graphitic Nanoribbons

Solid-state topochemical polymerization (SSTP) is a promising method to construct functional crystalline polymeric mate-rials, but contrast to various reactions happened in solution, only very limited types of SSTP reactions are reported. Diels-Alder (DA) and dehydro-DA (DDA) reaction are textbook reactions for preparing six-membered rings in solution, but scarcely seen in solid-state synthesis. Here, using multiple cutting-edge techniques, we demonstrate that the solid 1,4-diphenylbutadiyne (DPB) undergoes a DDA reaction under 10-20 GPa with the phenyl as the dienophile. The crystal structure at the critical pressure shows this reaction is “distance selected”. The distance of 3.2 Å between the phenyl and the phenylethynyl facilitates the DDA reaction, while the distances for other DDA and 1, 4-addition reactions are too large to allow the bonding. The obtained products are crystalline armchair graphitic nanoribbons, and hence our studies open a new route to construct the crystalline carbon materials with atomic-scale control.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Crystalline Order Yet Glass-Like Heat Transport Driven by Hidden Local Distortions as the Structural Origin of Ultralow Thermal Conductivity in AgErTe 2

Given their rich chemical diversity and the interplay among the p-, d-, and f-orbitals of chalcogens, transition metals, and lanthanides, respectively, rare-earth transition-metal chalcogenides exhibit a wide variety of structural, magnetic, and transport phenomena. As a result, they form a particularly appealing platform for investigating structure–property relationships, emergent electronic and magnetic behaviors, and thermal transport. Here we investigate AgErTe 2 as a model system to understand phonon-glass behavior in ordered crystalline solids, which establishes the design principles for thermal barrier coatings and next-generation thermoelectrics. The local bonding asymmetry and lattice softness suppress the inherently low lattice thermal conductivity, resembling the characteristics of amorphous materials. This suppression is significantly influenced by local off-centering of Ag atoms, which breaks lattice periodicity while maintaining global crystallinity. The presence of antibonding states just below the Fermi level, arising from Ag 4d and Te 5p orbital interactions, leads to lattice softening and destabilizes ideal tetrahedral coordination, resulting in a pseudo Jahn–Teller distortion. Furthermore, the coexistence of weaker, more polarizable Ag–Te bonds and stronger Er–Te bonds creates a complex vibrational landscape enriched with low-frequency modes and enhanced phonon scattering. A pronounced disparity in interatomic force constants gives rise to highly localized, low-energy optical phonons linked to Ag rattling. These flat vibrational modes exhibit strong coupling with transverse acoustic phonons, resulting in ultrashort phonon lifetimes and mean free paths approaching interatomic distances. These features collectively enhance phonon scattering across a broad range of length and energy scales. This work offers a framework for engineering suppressed thermal conductivity in crystalline systems without the introduction of alloying elements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Photonic time-crystalline behaviour mediated by phonon squeezing in T a 2 NiSe 5

Photonic time crystals refer to materials whose dielectric properties are periodic in time, analogous to a photonic crystal whose dielectric properties is periodic in space. Here, we theoretically investigate photonic time-crystalline behaviour initiated by optical excitation above the electronic gap of the excitonic insulator candidate Ta 2 NiSe 5 . We show that after electron photoexcitation, electron-phonon coupling leads to an unconventional squeezed phonon state, characterised by periodic oscillations of phonon fluctuations. Squeezing oscillations lead to photonic time crystalline behaviour. The key signature of the photonic time crystalline behaviour is terahertz (THz) amplification of reflectivity in a narrow frequency band. The theory is supported by experimental results on Ta 2 NiSe 5 where photoexcitation with short pulses leads to enhanced THz reflectivity with the predicted features. We explain the key mechanism leading to THz amplification in terms of a simplified electron-phonon Hamiltonian motivated by ab-initio DFT calculations. Our theory suggests that the pumped Ta 2 NiSe 5 is a gain medium, demonstrating that squeezed phonon noise may be used to create THz amplifiers in THz communication applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Liquid crystalline behavior and photoluminescence of lanthanide decanoate nanoparticles synthesized by microwave radiation

Luminescent lanthanide decanoate nanoparticles (LnC 10 NPs; Ln = Pr, Nd, Sm, Eu, Gd, Er) with spherical morphology (<100 nm) have been synthesized via a facile microwave (MWV) method using Ln(NO 3 ) 3 ·xH 2 O, ethanol/water, and decanoic acid. These hybrid nanomaterials adopt a lamellar structure consisting of inorganic Ln 3+ layers separated by a decanoate anion bilayer and exhibit liquid crystalline (LC) phases during melting. The particle size, crystalline structure, and LC behavior were characterized using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and powder X-ray diffraction (ambient and heated). Thermal analysis indicated the formation of Smectic A LC phases by LnC 10 nanoparticles, with the smaller lanthanides (Ln = Sm, Gd, Er) displaying additional solid intermediate and Smectic C phases. The formation of LC phases by the smaller Ln 3+ suggests that these nanoscale materials have vastly different thermal properties than their bulk counterparts, which do not exhibit LC behavior. In this work, photoluminescence spectroscopy revealed the LnC 10 NPs to be highly optically active, producing strong visible emissions that corresponded to expected electronic transitions by the various Ln 3+ ions. Under long-wave UV irradiation (λ = 365 nm), bright visible luminescence was observed for colloidal suspensions of Nd, Sm, Eu, Gd, and ErC 10 NPs. To the best of the authors’ knowledge, this is the first reported synthesis of nanoscale metal alkanoates, the first report of liquid crystalline behavior by any decanoate of lanthanides smaller than Nd, and the first observation of strong visible luminescence by non-vitrified lanthanide alkanoates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

An in situ formed inorganic conductive network enables high stability and rate capability of single-crystalline nickel-rich cathodes

Single-crystalline Ni-rich cathodes are promising for the next generation of high-energy-density Li-ion batteries due to their better capacity retention than their polycrystalline counterparts. However, there is still much room for improving the electrochemical performances when considering their surface degradation and severe kinetic hindrance during cycling. Herein, we report a strategy to construct an in situ formed robust Li-conductive Li 3 PO 4 layer on the surface of cathode particles. This Li-conductive layer significantly increases the Li-ion diffusion coefficients and suppresses detrimental surface phase transformation. In situ XRD reveals that the improved kinetics alleviate the local stress at high voltage. The as-prepared single-crystalline LiNi 0.83 Co 0.12 Mn 0.05 O 2 delivers good durability (96.8% after 100 cycles at 1C) and excellent rate capability (177.08 mA h g -1 at 5C). Here, this work provides a facile and efficient strategy to improve the cycling performance and boost the rate capability of single-crystalline Ni-rich cathodes.

25 ENERGY STORAGE↗
DOE OSTI2025

Evolution of silicate coordination in architected amorphous and crystalline magnesium silicates during carbon mineralization

Advancing durable solutions for carbon storage and removal at the gigaton scale to produce solid carbonates via carbon mineralization requires harnessing earth abundant magnesium silicate resources. Calibrated insights linking the structural and morphological features of earth abundant amorphous and crystalline magnesium silicate phases to their reactivity are essential for scalable deployment but remain underdeveloped. To resolve the influence of silica coordination and mass transfer on carbon mineralization behavior, magnesium silicates bearing amorphous and crystalline phases (AC Mg-silicate) are synthesized. The structural and morphological transitions starting from colloidal precursors to their final synthesized form on heating are delineated using operando ultra small/small/wide angle X-ray scattering (USAXS/SAXS/WAXS) measurements. The evolution of the silicate phases on carbon mineralization of AC Mg-silicate is contrasted with that of highly crystalline Mg-silicate (HC Mg-silicate) when reacted at 200 °C and a CO 2 partial pressure of 20 atm in water and 1 M NaHCO 3 solution in stirred and unstirred environments. These experimental conditions are analogous to those of the water–gas-shift reaction for sustainable recovery of H 2 with inherent carbon mineralization. Enhancement in the extent of carbon mineralization by 13.3–19.5% noted in the presence of NaHCO 3 compared to water in AC and HC Mg-silicate with and without stirring, is attributed to the buffering effect which aids simultaneous silicate dissolution and carbon mineralization. Enhanced extents of carbon mineralization in the presence of NaHCO 3 correspond to the formation of MgSiO 3 and SiO 2 phases from the starting Mg 2 SiO 4 precursors in AC and HC Mg-silicate. Unlocking these silicate transformations during carbon mineralization by harnessing architected Mg-silicate precursors reveals the feasibility of integrating these chemical pathways with sustainable H 2 conversion pathways with inherent carbon mineralization.

Gao, Xun [Cornell Univ., Ithaca, NY (United States↗
DOE OSTI2025

Elucidating the reversible exsolution–dissolution behaviour of high-entropy oxides in crystalline and amorphous phases

High-entropy oxides (HEOs), as a subclass of high-entropy materials (HEMs), offer a versatile platform for catalysis by leveraging entropy-stabilized solid solutions with tunable compositions, lattice structures, and electronic properties. While exsolution–dissolution of metal species in crystalline HEOs has emerged as a promising strategy for reversible active sites regeneration, the dynamic behaviour of HEOs possessing amorphous nature remains under-explored, particularly the difference with crystalline counterparts. In this work, we systematically investigate the architecture-dependent exsolution–dissolution behavior of HEOs by comparing a crystalline-phase HEO (c-HEO) and an amorphous-phase HEO (a-HEO), both comprising Ni, Mg, Cu, Zn, and Co as principal metal elements. Using a combination of in situ variable-temperature X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy, and in situ CO diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS), the structural evolution of the two HEO phases under redox conditions was elucidated. Both materials exhibit reversible exsolution of metallic species or alloys in reducing environments, followed by re-incorporation into the host lattice upon oxidation. Remarkably, the a-HEO demonstrates more facile and dynamic self-healing behavior, with alloy exsolution and dissolution occurring under milder conditions because of its enhanced reducibility and structural disorder. This study provides critical insights into the design of next-generation regenerable catalysts based on amorphous HEOs, highlighting the role of phase structure in governing reversible metal-site formation dynamics and catalytic performance.

Wang, Qingju [Univ. of Tennessee, Knoxville, TN (U↗
DOE OSTI2021

Compositional and phase dependence of elastic modulus of crystalline and amorphous Hf 1- x Zr x O 2 thin films

The elastic moduli of amorphous and crystalline atomic layer-deposited Hf 1-x Zr x O 2 (HZO, x = 0, 0.31, 0.46, 0.79, 1) films prepared with TaN electrodes on silicon substrates were investigated using picosecond acoustic measurements. The moduli of the amorphous films were observed to increase between 211 ± 6 GPa for pure HfO 2 and 302 ± 9 GPa for pure ZrO 2 . In the crystalline films, it was found that the moduli increased upon increasing the zirconium composition from 248 ± 6 GPa for monoclinic HfO 2 to 267 ± 9 GPa for tetragonal ZrO 2 . Positive deviations from this increase were observed for the Hf 0.69 Zr 0.31 O 2 and Hf 0.54 Zr 0.46 O 2 compositions, which were measured to have moduli of 264 ± 8 GPa and 274 ± 8 GPa, respectively. These two compositions contained the largest fractions of the ferroelectric orthorhombic phase, as assessed from polarization and diffraction data. The biaxial stress states of the crystalline films were characterized through sin 2 (ψ) x-ray diffraction analysis. The in-plane stresses were all found to be tensile and observed to increase with the increasing zirconium composition, between 2.54 ± 0.6 GPa for pure HfO 2 and 5.22 ± 0.5 GPa for pure ZrO 2 . The stresses are consistent with large thermal expansion mismatches between the HZO films and silicon substrates. Furthermore, these results demonstrate a device-scale means to quantify biaxial stress for investigation on its effect on the ferroelectric properties of hafnia-based materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The anisotropic nature of singlet fission in single crystalline organic semiconductors

The escalating global energy predicament implores for a revolutionary resolution—one that converts sunlight into electricity—holding the key to supreme conversion efficiency. This comprehensive review embarks on the exploration of the principle of generating multiple excitons per absorbed photon, a captivating concept that possesses the potential to redefine the fundamental confines of conversion efficiency, albeit its application remains limited in photovoltaic devices. At the nucleus of this phenomenon are two principal processes: multiple exciton generation (MEG) within quantum-confined environments, and singlet fission (SF) inside molecular crystals. The process of SF, characterized by the cleavage of a single photogenerated singlet exciton into two triplet excitons, holds promise to potentially amplify photon-to-electron conversion efficiency twofold, thereby laying the groundwork to challenge the detailed balance limit of solar cell efficiency. Our discourse primarily dissects the complex nature of SF in crystalline organic semiconductors, laying special emphasis on the anisotropic behavior of SF and the diffusion of the subsequent triplet excitons in single-crystalline polyacene organic semiconductors. We initiate this journey of discovery by elucidating the principles of MEG and SF, tracing their historical genesis, and scrutinizing the anisotropy of SF and the impact of quantum decoherence within the purview of functional mode electron transfer theory. We present an overview of prominent techniques deployed in investigating anisotropic SF in organic semiconductors, including femtosecond transient absorption microscopy and imaging as well as stimulated Raman scattering microscopies, and highlight recent breakthroughs linked with the anisotropic dimensions of Davydov splitting, Herzberg–Teller effects, SF, and triplet transport operations in single-crystalline polyacenes. Through this comprehensive analysis, our objective is to interweave the fundamental principles of anisotropic SF and triplet transport with the current frontiers of scientific discovery, providing inspiration and facilitating future ventures to harness the anisotropic attributes of organic semiconductor crystals in the design of pioneering photovoltaic and photonic devices.

Chemistry↗
DOE OSTI2024

Fermiology and transport properties of the candidate topological crystalline insulator SrAg 4 ⁢Sb 2

Compared to time-reversal symmetry-protected ℤ 2 topological insulators and Dirac/Weyl semimetals, there are significantly fewer candidates for topological crystalline insulators. SrAg 4 ⁢Sb 2 is predicted to exhibit topological crystalline insulator behavior when considering spin-orbit coupling. In this study, we systematically investigate single crystals of SrAg 4 ⁢Sb 2 using electrical transport and magnetic torque measurements, along with first-principles calculations. Our transport data reveals its compensated semimetal nature with a magnetoresistance up to around 700% at 2 K and 9 T. Analysis of de Haas–van Alphen oscillations uncovers a Fermi surface consisting of three distinct Fermi pockets with light effective masses. Comparison between the three-dimensional fermiology obtained from our oscillation data and the first-principles calculations demonstrates excellent agreement. This confirms the accuracy of the calculations, which indicate a band inversion centered at the 𝑇 point and identify the existence of nontrivial tube and needle hole Fermi pockets at Γ, alongside one trivial diamond electron pocket at the 𝐹 point in the Brillouin zone. Furthermore, symmetry and topology analysis results in two potential sets of topological invariants, suggesting the emergence of two-dimensional gapless Dirac surface states either on the 𝑎⁢𝑏 planes or on both the 𝑎⁢𝑏 planes and mirror planes, protected by crystal symmetries. Therefore, SrAg 4 ⁢Sb 2 emerges as a promising candidate topological crystalline insulator.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Development of a scalar-based geometric parameterization approach for the crystal structure landscape of dithienylethene-based crystalline solids

Dithienylethenes (DTEs) are a promising class of organic photoswitches that can be used to create crystalline solids with properties controlled by light. However, the ability of DTEs to adopt multiple conformations, only one of which is photoactive, complicates the rational design of these materials. Herein, the synthesis and structural characterization of 19 crystalline solids containing a single DTE molecule are described. A novel D – D analysis of the molecular geometries obtained from rotational potential energy surface calculations and the ensemble of experimental structures were used to construct a crystal landscape for DTE. Of the 19 crystal structures, 17 contained photoinactive DTE rotamers and only 2 were photoactive. These results highlight the challenges associated with the design of these materials. Overall, the D – D analysis described herein provides rapid, effective and intuitive means of linking the molecular structure to photoactivity that could be applied more broadly to afford a general strategy for producing photoactive diarylethene-based crystalline solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗