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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Measurements of density, temperature, and their fluctuations in turbulent supersonic flow using UV laser spectroscopy

Nonintrusive measurements of density, temperature, and their turbulent fluctuation levels were obtained in the boundary layer of an unseeded, Mach 2 wind tunnel flow. The spectroscopic technique that was used to make the measurements is based on the combination of laser-induced oxygen fluorescence and Raman scattering by oxygen and nitrogen from the same laser pulse. Results from this demonstration experiment are compared with previous measurements obtained in the same facility using conventional probes and an earlier spectroscopic technique. Densities and temperatures measured with the current technique agree with the previous surveys to within 3 percent and 2 percent, respectively. The fluctuation amplitudes for both variables agree with the measurements obtained using the earlier spectroscopic technique and show evidence of an unsteady, weak shock wave that perturbs the boundary layer.

Fletcher, Douglas G.↗
DOE OSTI2023

Space-Time Quantum Information from the Entangled States of Magnetic Molecule (STI Product)

This collaborative project combines synthesis, measurement, and theory by three faculty members at the Eddleman Quantum Institute of UC Irvine to effectively investigate the quantum properties of molecules in the space, time, and frequency domains. Through synthetic chemistry, molecules are tailored for their magnetic and coherent properties. By combining femtosecond (fs) terahertz (THz) light and a continuous wave (cw) THz laser with a low temperature scanning tunneling microscope (STM), quantum phenomena are probed with simultaneous femtosecond temporal and atomic-scale spatial resolution. In particular, the invention of the quantum superposition microscope (QSM) advances quantum sensing for enhanced spectroscopy and imaging capabilities. Coupling theory to the experimental efforts offers a deeper understanding and predictive power for the molecular systems. The phenomena of superposition, entanglement, and coherence is central to quantum information science and can be realized in qubit states. Many systems can be modeled by a double-well potential in which two levels are formed in the two lowest energy states interacting with the environment and external radiation. In focusing on molecules as two-level systems, the underlying expectation is that their tunable composition and structure allows an effective parameter space to optimize their use as qubits for quantum sensing and computing. The THz radiation induces the superposition between the two states, appearing as temporal oscillations that damp in amplitude. Enhanced spectroscopy and imaging in the time and frequency domains is achieved through the extreme sensitivity of the frequency and damping of coherence of two-level systems to its environment. A single hydrogen molecule trapped in the STM tunneling gap experiences a double-well potential and absorption of THz femtosecond pulses of light creates the superposition of its two levels, appearing as damped oscillations in the light induced direct current (DC). The oscillation frequency depends sensitively on the electric field distribution of the copper nitride (Cu 2 N) surface, through the Stark effect, and associated with the different charge distributions at the copper and nitrogen sites and in between. This QSM can resolve variation in the surface electric field with 0.02 nanometer resolution. In addition, the single hydrogen molecule entaes with nearby hydrogen molecules as seen in the avoided level crossings of energy (oscillation frequency) versus the voltage across the tunneling gap. Thus, the first application of the QSM senses and images the surface electric field at the atomic scale. Results from this project advance fundamental understanding of quantum phenomena, develop novel synthesis, measurement, and theory, provide the knowledge foundation for molecule-based qubits and sensing that enable the development of the QSM and emergent technologies. This project trained researchers in quantum information science, extended knowledge in classrooms, and outreached to the community.

47 OTHER INSTRUMENTATION↗
NASA NTRS1992

Single-pulse measurement of density and temperature in a turbulent, supersonic flow using UV laser spectroscopy

Nonintrusive measurements of density and temperature and their turbulent fluctuation levels have been obtained in the boundary layer of an unseeded, Mach 2 wind tunnel flow. The spectroscopic technique that was used to make the measurements is based on the combination of laser-induced oxygen fluorescence and Raman scattering by oxygen and nitrogen from the same laser pulse. Results from this demonstration experiment compare favorably with previous measurements obtained in the same facility from conventional probes and an earlier spectroscopic technique.

Fletcher, D. G.↗
DOE OSTI2026

Strain-Modified Raman Responses in Monolayer MoS 2 Nanobubbles Resolved at 5 nm

The formation of nanoscale bubbles is an unavoidable consequence during the transfer of two-dimensional materials onto target substrates, driven by van der Waals interactions at the interface. While often viewed as imperfections, these nanoscale bubbles have garnered considerable scientific interest due to the substantial in-plane strain gradients they induce, which in turn give rise to a variety of intriguing optoelectronic effects, particularly in semiconducting transition metal dichalcogenides. Determining and analyzing the strain distribution within nanobubbles at the nanoscale is crucial for advancing our understanding of these underlying strain-induced effects. Here, we present a high-resolution scanning tunneling microscopy-based tip-enhanced Raman spectroscopic investigation of localized nanoscale strain distribution within the nanobubbles formed between monolayer MoS 2 and Au interface. By employing cryogenic temperature (78 K), we successfully differentiate the nanoscale Raman signatures between nanobubble edge and pristine MoS 2 . We verify a maximum tensile strain of ∽1.15–1.34% at the nanobubble edge, which gradually diminishes toward the center, yielding a cross-sectional strain profile consistent with a doughnut-shaped distribution. Furthermore, we report to achieve ∽5 nm spatial resolution in probing such edge-localized strain within the nanobubble. In addition, comparative average strain analysis of such MoS 2 nanobubbles is conducted via geometric mechanistic analysis such as membrane and nonlinear plate theories, providing key insight into the geometric nature near the bubble edge. Our work provide fundamental information about strain-induced nanoscale chemical understanding of 2D materials on the nanometer scale, paving the way for practical applications of nanobubbles in strain-engineered optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

In-situ observation of trapped carriers in organic metal halide perovskite films with ultra-fast temporal and ultra-high energetic resolutions

Abstract We in-situ observe the ultrafast dynamics of trapped carriers in organic methyl ammonium lead halide perovskite thin films by ultrafast photocurrent spectroscopy with a sub-25 picosecond time resolution. Upon ultrafast laser excitation, trapped carriers follow a phonon assisted tunneling mechanism and a hopping transport mechanism along ultra-shallow to shallow trap states ranging from 1.72–11.51 millielectronvolts and is demonstrated by time-dependent and independent activation energies. Using temperature as an energetic ruler, we map trap states with ultra-high energy resolution down to < 0.01 millielectronvolt. In addition to carrier mobility of ~4 cm 2 V −1 s −1 and lifetime of ~1 nanosecond, we validate the above transport mechanisms by highlighting trap state dynamics, including trapping rates, de-trapping rates and trap properties, such as trap density, trap levels, and capture-cross sections. In this work we establish a foundation for trap dynamics in high defect-tolerant perovskites with ultra-fast temporal and ultra-high energetic resolution.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Measurements of a supersonic velocity in a nitrogen flow using inverse Raman spectroscopy

Results are presented for supersonic molecular flow-velocity measurements using inverse Raman spectroscopy. The flow velocity, temperature, and density of flowing N2 molecules are measured because of potential wind-tunnel applications. Uncertainties of less than 5% are found for the velocity measurements, while the uncertainties are about 10% for the temperature and density measurements. The laser probe is stabilized by using I2 fluorescence, and I2 saturated absorption is utilized to provide an absolute frequency reference. Differential detection techniques are employed to reduce detection noise.

Herring, G. C.↗
DOE OSTI2026

Kramers nodal line in the charge density wave state of YTe 3 and the influence of twin domains

Recent studies have focused on the relationship between charge density wave (CDW) collective electronic ground states and nontrivial topological states. YTe 3 , a nonmagnetic quasi-two-dimensional chalcogenide, has been reported to exhibit a CDW state below 334 K. Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), we establish that YTe 3 is a CDW-induced Kramers nodal line (KNL) metal, a recently proposed topological state of matter. Scanning tunneling microscopy and low energy electron diffraction reveal two orthogonal domains, each with a unidirectional CDW and a similar wave vector (𝐪 CDW ). When the influence of twin domains is considered, the effective band structure (EBS) computations that utilize DFT-calculated bands using a noncentrosymmetric structure determined by x-ray crystallography, show excellent agreement with ARPES. The noncentrosymmetry of YTe 3 is established by Raman spectroscopy. The Fermi surface and ARPES intensity plots show weak shadow bands displaced by 𝐪 CDW from the main bands. Furthermore, these are linked to CDW modulation, as the EBS calculation confirms. Bilayer split main and shadow bands suggest the existence of crossings, according to theory and experiment. DFT bands, including spin-orbit coupling, indicate existence of a KNL along the Σ direction from multiple crossings of bands dispersing perpendicular to it. Additionally, doubly degenerate bands are only found along the KNL at all energies, with some bands dispersing through the Fermi level.

Angle-resolved photoemission spectroscopy↗
DOE OSTI2025

Interplay Between Stereochemically Active Lone Pair Repulsions, Sigma Hole Interactions, and Delocalized Redox Processes in Topochemical Fluoride‐Ion Insertion

Topochemical insertion/extraction of cations has emerged as a generalizable strategy for modulating the crystal and electronic structure of periodic solids. In contrast, strategies for topochemical anion insertion are poorly explored and fundamental principles for designing insertion hosts to accommodate anions remain scarce. Here, we observe reversible room-temperature fluoride-ion insertion within tunnels of Sn 2 TiO 4 defined by the stereochemical expression of Sn 5 s 2 lone pairs. X-ray scattering studies of fluoride-ion-insertion-induced crystal structure modulation and X-ray absorption/emission spectroscopy probes of electronic structure along with magnetic susceptibility measurements and first-principles calculations are used to decipher design principles underpinning reversible fluoride-ion insertion and bulk diffusion. Fluoride-ion insertion is enabled by a combination of a large, polarizable tunnel, delocalized redox at Ti─O─Sn centers, inherent repulsion between the fluoride-ion and Sn 5 s 2 electron lone pairs, and the formation of dative interactions between Sn-centered σ-holes and fluoride-ions, yielding a reversible capacity of 0.5 fluoride-ions per Sn 2 TiO 4 formula unit. Our results demonstrate that the complex interplay between dative interactions and stereochemically active lone pair repulsions is critical to defining the thermodynamics and kinetics controlling fluoride-ion insertion and diffusion. As such, the design of fluoride-ion insertion hosts for anion batteries requires site-selective modification to modulate lattice—ion interactions.

36 MATERIALS SCIENCE↗
DOE OSTI2024

An alcove at the acetyl-CoA synthase nickel active site is required for productive substrate CO binding and anaerobic carbon fixation

One of the seven natural CO 2 fixation pathways, the anaerobic Wood-Ljungdahl pathway (WLP) is unique in generating CO as a metabolic intermediate, operating through organometallic intermediates, and in conserving (versus utilizing) net ATP. The key enzyme in the WLP is acetyl-CoA synthase (ACS), which uses an active site [2Ni-4Fe-4S] cluster (A-cluster), a CO tunnel, and an organometallic (Ni-CO, Ni-methyl, and Ni-acetyl) reaction sequence to generate acetyl-CoA. Here, we reveal that an alcove, which interfaces the tunnel and the A-cluster, is essential for CO 2 fixation and autotrophic growth by the WLP. In vitro spectroscopy, kinetics, binding, and in vivo growth experiments reveal that a Phe229A substitution at one wall of the alcove decreases CO affinity thirty-fold and abolishes autotrophic growth; however, a F229W substitution enhances CO binding 80-fold. Our results indicate that the structure of the alcove is exquisitely tuned to concentrate CO near the A-cluster; protect ACS from CO loss during catalysis, provide a haven for inhibitory CO, and stabilize the tetrahedral coordination at the Nip site where CO binds. The directing, concentrating, and protective effects of the alcove explain the inability of F209A to grow autotrophically. The alcove also could help explain current controversies over whether ACS binds CO and methyl through a random or ordered mechanism. Our work redefines what we historically refer to as the metallocenter "active site". The alcove is so crucial for enzymatic function that we propose it is part of the active site. The community should now look for such alcoves in all "gas handling" metalloenzymes.

bacterial metabolism↗
DOE OSTI2021

Exotic Long-Range Surface Reconstruction on La 0.7 Sr 0.3 MnO 3 Thin Films

Due to an extremely diverse phase space, La 1–x Sr x MnO 3 , as with other manganites, offers a wide range of tunability and applications including colossal magnetoresistance and use as spin-polarized electrodes. Here, we study an unprecedented, exotic surface reconstruction (6 × 6) in La 1–x Sr x MnO 3 (x = 0.3) observed via low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) shows the surface is relatively flat, with unit-cell step heights, and X-ray photoelectron spectroscopy (XPS) reveals a strong degree of Sr segregation at the surface. By combining electron diffraction and first-principles computations, we propose that the long-range surface reconstruction consists of a Sr-segregated surface with La (6 × 6) ordering. This study expands our understanding of manganite systems and underscores their ability to form interesting surface reconstructions, driven largely by cation segregation that can potentially be controlled for tuning surface ordering.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A cleanroom in a glovebox

The exploration of new materials, novel quantum phases, and devices requires ways to prepare cleaner samples with smaller feature sizes. Initially, this meant the use of a cleanroom that limits the amount and size of dust particles. However, many materials are highly sensitive to oxygen and water in the air. Furthermore, the ever-increasing demand for a quantum workforce, trained and able to use the equipment for creating and characterizing materials, calls for a dramatic reduction in the cost to create and operate such facilities. To this end, we present our cleanroom-in-a-glovebox, a system that allows for the fabrication and characterization of devices in an inert argon atmosphere. Additionally, we demonstrate the ability to perform a wide range of characterization as well as fabrication steps, without the need for a dedicated room, all in an argon environment. Finally, we discuss the custom-built antechamber attached to the back of the glovebox. This antechamber allows the glovebox to interface with ultra-high vacuum equipment such as molecular-beam epitaxy and scanning tunneling microscopy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

First-Principles Assessment of ZnTe and CdSe as Prospective Tunnel Barriers at the InAs/Al Interface

Majorana zero modes are predicted to emerge in semiconductor/ superconductor interfaces, such as InAs/Al. Majorana modes could be utilized for fault tolerant topological qubits. However, their realization is hindered by materials challenges. The coupling between the superconductor and the semiconductor may be too strong for Majorana modes to emerge, due to effective doping of the semiconductor by the metallic contact. This could be mediated by adding a tunnel barrier of controlled thickness. We use density functional theory (DFT) with Hubbard U corrections, whose values are machine-learned via Bayesian optimization (BO), to assess ZnTe and CdSe as prospective tunnel barriers for the InAs/Al interface. The results of DFT +U(BO) for ZnTe are validated by comparison to angle resolved photoemission spectroscopy (ARPES). We then study bilayer interfaces of the three semiconductors with each other and with Al, as well as trilayer interfaces with a varying number of ZnTe or CdSe layers inserted between InAs and Al. We find that 16 atomic layers of either material completely insulate the InAs from metal induced gap states (MIGS). However, ZnTe and CdSe differ significantly in their band alignment, such that ZnTe forms an effective barrier for electrons, whereas CdSe forms a barrier for holes. Because of Fermi level pinning in the conduction band at the interface, only electron transport is relevant for InAs-based Majorana devices. Therefore, ZnTe is the better choice. Based on the results of our simulations, we suggest conducting experiments with ZnTe barriers in the thickness range of 6–18 atomic layers.

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

Correlating structure, self-assembly chemistry and conductivity of trithiocyanuric acid on Au(111)

The majority of candidates for simple model molecular-electronic components consist of a conductive π-conjugated hydrocarbon linker attached to at least two anchoring groups, such as thiols or isocyanides. It has been found that select molecules self-assemble on gold surfaces, creating one-dimensional conductive structures that act as “molecular wires”. Furthermore, these oligomers can form molecular bridges between gold nanoparticles, leading to the creation of simple molecular-electronic devices. This raises the question whether other π-conjugated molecular linkers could exhibit similar behavior that might offer a broader range of candidates for fabricating electronic devices. Trithiocyanuric acid (1,3,5-triazine-2,4,6-trithiol, TTCA) provides a possible candidate. TTCA (C3N3(SH)3) can exist as a trithiol or as a trithione in which hydrogens transfer to the sulfurs so that they are present with three C=N groups within the ring. TTCA exists naturally in the trithione form but converts into a trithiol when adsorbed onto an Ag(111) where it is vertically oriented. The structure of TTCA adsorbed on Au(111) is studied here using reflection-absorption infrared spectroscopy (RAIRS) where it is found to remain as the trithione isomer, but changes orientation as the coverage increases. Scanning-tunneling microscopy (STM) reveals that TTCA oligomerizes on Au(111) to form chains and triangular structures. The influence on molecular conductivity due to the differences in the adsorbate's isomeric structure was investigated using devices comprising either silver or gold nanoparticles deposited in the gap between gold nanoelectrodes. Both devices were found to conduct when dosed with TTCA, but the devices fabricated using silver were about 13 time more conductive than those made from gold nanoparticles, consistent with the π-conjugated structure formed on silver but not on gold. This implies that oligomers form both on silver and on gold and potentially increases the range of molecule-metal combinations that might be used to fabricate molecular-electronic devices.

Molecular electronics↗
DOE OSTI2024

Ferromagnetic Exchange and Slow Magnetic Relaxation in Cobalt Bis(1,2-dithiolene)-Bridged Dilanthanide Complexes

The construction of multinuclear lanthanide-based molecules with significant magnetic exchange interactions represents a key challenge in the realization of single-molecule magnets with high operating temperatures. Here, we report the synthesis and magnetic characterization of two series of heterobimetallic compounds, (Cp* 2 Ln) 2 (μ-Co(pdt) 2 ) (Ln = Y 3+ , Gd 3+ , Dy 3+ ; pdt 2– = 1,2-diphenylethylenedithiolate) and [K(18-crown-6)][(Cp* 2 Ln) 2 (μ-Co(pdt) 2 )] (Ln = Y 3+ , Gd 3+ ), featuring two lanthanide centers bridged by a cobalt bis(1,2-dithiolene) complex. Dc magnetic susceptibility data collected for the Gd congeners indicate significant Gd–Co ferromagnetic exchange interactions with fits affording J = +11.5 and +7.33 cm –1 , respectively. Magnetization decay and ac magnetic susceptibility measurements carried out on the single-molecule magnet (Cp* 2 Dy) 2 (μ-Co(pdt) 2 ) reveal full suppression of quantum tunneling and open-loop hysteresis persisting up to 3.5 K. These results, along with those of high-field EPR spectroscopy, suggest that transition metalloligands can enforce strong exchange interactions with adjacent lanthanide centers while maintaining a geometry that preserves molecular anisotropy. Furthermore, the magnetic properties of [K(18-crown-6)][(Cp* 2 Gd) 2 (μ-Co(pdt) 2 )] show that increasing the spin of the ground state of the bridging complex may be a viable alternative to increasing J in obtaining well-isolated, strongly coupled magnetic ground states.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Surface superconductivity in the type II Weyl semimetal TaIrTe 4

The search for unconventional superconductivity in Weyl semimetal materials is currently an exciting pursuit, since such superconducting phases could potentially be topologically non-trivial and host exotic Majorana modes. The layered material TaIrTe 4 is a newly predicted time-reversal invariant type II Weyl semimetal with the minimum number of Weyl points. Here, we report the discovery of surface superconductivity in Weyl semimetal TaIrTe 4 . Our scanning tunneling microscopy/spectroscopy (STM/STS) visualizes Fermi arc surface states of TaIrTe 4 that are consistent with the previous angle-resolved photoemission spectroscopy results. By a systematic study based on STS at ultralow temperature, we observe uniform superconducting gaps on the sample surface. The superconductivity is further confirmed by electrical transport measurements at ultralow temperature, with an onset transition temperature (T c ) up to 1.54 K being observed. The normalized upper critical field h*(T/T c ) behavior and the stability of the superconductivity against the ferromagnet indicate that the discovered superconductivity is unconventional with the p-wave pairing. The systematic STS, and thickness- and angular-dependent transport measurements reveal that the detected superconductivity is quasi-1D and occurs in the surface states. The discovery of the surface superconductivity in TaIrTe 4 provides a new novel platform to explore topological superconductivity and Majorana modes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1994

The effect of Low Earth Orbit exposure on some experimental fluorine and silicon-containing polymers

Several experimental fluorine and silicon-containing polymers in film form were exposed to low Earth orbit (LEO) on a Space Shuttle flight experiment (STS-46, Evaluation of Oxygen Interaction with Materials, EOIM-3). The environmental parameters of primary concern were atomic oxygen (AO) and ultraviolet (UV) radiation. The materials were exposed to 2.3 plus or minus 0.1 x 10(exp 20) oxygen atoms/sq cm and 30.6 UV sun hours during the flight. In some cases, the samples were exposed at ambient, 120 C and 200 C. The effects of exposure on these materials were assessed utilizing a variety of characterization techniques including optical, scanning electron (SEM) and scanning tunneling (STM) microscopy, UV-visible (UV-VIS) transmission, diffuse reflectance infrared (DR-FTIR), x-ray photoelectron (XPS) spectroscopy, and in a few cases, gel permeation chromatography (GPC). In addition, weight losses of the films, presumably due to AO erosion, were measured. The fluorine-containing polymers exhibited significant AO erosion and exposed films were diffuse or 'frosted' in appearance and consequently displayed dramatic reductions in optical transmission. The silicon-containing films exhibited minimum AO erosion and the optical transmission of exposed films was essentially unchanged. The silicon near the exposed surface in the films was converted to silicate/silicon oxide upon AO exposure which subsequently provided protection for the underlying material. The silicon-containing epoxies are potentially useful as AO resistant coatings and matrix resins as they are readily processed into carbon fiber reinforced composites and cured via electron radiation.

Connell, John W.↗
DOE OSTI2024

Co-deposition of bismuth-nitrogen films on MgO (001) by molecular beam epitaxy

Here, we attempted to grow a thin film of BiN by co-deposition of bismuth and nitrogen on rock-salt structure MgO (001) substrates. Furthermore, we studied the effect of variation of the growth temperature and the nitrogen to bismuth flux ratios on sample growth. For the samples grown and conditions used, we do not find strong evidence for the formation of a bulk Bi-N alloy. Even for very high nitrogen to bismuth flux ratio, we observed only bismuth and no nitrogen using bulk Rutherford back-scattering spectroscopy measurements, and only 1%–2% nitrogen was seen through surface Auger electron spectroscopy measurements. The in-plane lattice measurements show that the resulting Bi (110) samples are strained, which is presumably caused by lattice mismatch between the sample and the substrate when grown without any buffer layer. The use of a high-temperature buffer layer helps to release strain in the sample but only along one axis. Measurements of the atomic layer spacing using x-ray diffraction and also scanning tunneling microscopy confirm the Bi (110) thin film sample structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

An Atom-Precise Approach to Damp First-Order Phase Transitions and Its Implications for Neuromorphic Signal Processing

Neuromorphic computing inspired by mammalian intelligence aims to emulate the nonlinear dynamics of biological neurons and synapses to achieve fast, low-energy, and highly efficient information processing. Brain-inspired computing relies on the design and discovery of materials exhibiting nonlinear current–voltage profiles, frequently underpinned by electronic state transitions, to achieve spiking neurons and dynamically tunable synapses. A signature challenge in the design of artificial neurons is controlling the steepness of first-order transitions in active elements, as abrupt transitions are at risk of driving unstable voltage and temperature oscillations, which result in catastrophic device failure. A critical knowledge gap is the lack of structure–function correlations mapping the composition and atomistic structure of crystalline solids to nonlinear dynamical response characteristics. Here, we address the key question of how modification of atomistic structure correlates with alteration of neuron-like functionality. Constructing oscillator circuits from millimeter-scale single crystals enables high-resolution atomic structure solutions, which we use to demonstrate that the selective positioning of Pb cations modifies charge ordering along a one-dimensional CuxV2O5 framework even at low insertion stoichiometries, thereby providing an atom-precise design parameter for damping first-order transitions. We use temperature-variant X-ray diffraction and X-ray spectroscopy to elucidate the suppression of Cu-ion shuttling based on the precise positioning of Pb ions in seven-coordinated tunnel interstitial sites as the mechanistic basis for transition broadening, thus bridging a critical gap between statistical mechanics and quantum chemical descriptions of phase transitions. Such mechanistic understanding thus paves the way to site-selective modification strategies for modulating the sharpness of first-order transitions, with an exemplary demonstration here in tuning neuronal signal processing.

Crystal structure↗