I11-High Resolution Powder Diffraction
|
Frederic
Rendell-Bhatti
,
Melony
Dilshad
,
Celine
Beck
,
Markus
Appel
,
Alba
Prats
,
Eamonn T.
Connolly
,
Claire
Wilson
,
Lewis
Giannelli
,
Pol
Lloveras
,
Xavier
Moya
,
David
Boldrin
,
Donald A.
Maclaren
Diamond Proposal Number(s):
[40567]
Open Access
Abstract: The discovery of colossal barocaloric effects in neopentyl glycol (NPG) makes plastic crystals promising candidates for solid-state refrigerants with lower environmental impact than vapour compression fluids. Optimising operational temperatures and low-pressure operability remains challenging without compromising thermodynamic parameters. Here, we implement a strategy to improve the viability of NPG derivatives as barocaloric refrigerants. We blend pentaglycerine (PG) with NPG to lower the phase transition temperature, then dope the blend with 2% pentaerythritol (PE) to improve transition reversibility. In comparison with NPG under the same conditions, this ternary system has a seven-fold increase in reversible isothermal entropy change ( = 13.4 J kg−1 K−1) and twenty-fold increase in operational temperature span ( = 18 K) at pressures of 1 kbar. Synchrotron x-ray diffraction and quasielastic neutron scattering reveal structural and dynamical effects that broaden the temperature range of the first-order phase transition due to intermolecular hydrogen bond network disruption by the molecular dopants. We propose that exploiting the compositional phase space of multi-component molecular blends is effective for designing practicable molecular BCs.
|
Jan 2026
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
|
Sam
Riley
,
Antonios
Vamvakeros
,
Gustavo
Quino
,
John
Morley
,
Mengzheng
Ouyang
,
Andrew
Shevchuk
,
Kehan
Huang
,
Pierre-Olivier
Autran
,
Stefan
Michalik
,
Genoveva
Burca
,
Billy
Wu
,
Nigel
Brandon
,
Chandramohan
George
Diamond Proposal Number(s):
[36699]
Open Access
Abstract: Understanding the strain tolerance of both standard and mechanically flexible battery electrodes is prerequisite for optimizing performance, safety, and longevity, particularly in heavy-duty applications, flexible electronics and wearables. Achieving this requires a deeper understanding of how mechanical strain drives electrode degradation. In this work, we directly compare the strain response of electrospun (flexible) and slurry-cast (conventional) electrodes. To simulate acute mechanical stress, electrodes underwent a controlled 180° folding, pressing, and unfolding protocol designed to induce measurable damage, we then employed a combination of characterization techniques, including synchrotron X-ray nano-computed tomography, X-ray diffraction mapping, electrochemical analysis, and in situ Tensiometer-scanning electron microscopy to assess both structural and electrochemical degradation modes and provide a standardised upper-bound for strain induced damage. Our results reveal that electrospun electrodes exhibit significantly greater resilience to deformation, attributed to their freestanding architecture and fibrous morphology. These findings underscore the importance of characterizing deformation mechanisms to guide the design of high-performance batteries.
|
Jan 2026
|
|
I05-ARPES
|
I.
Biało
,
Qisi
Wang
,
J.
Küspert
,
X.
Hong
,
L.
Martinelli
,
O.
Gerguri
,
Y.
Chan
,
K.
Von Arx
,
O. K.
Forslund
,
W. R.
Pudełko
,
C.
Lin
,
N. C.
Plumb
,
Y.
Sassa
,
D.
Betto
,
N. B.
Brookes
,
M.
Rosmus
,
N.
Olszowska
,
Ma. D.
Watson
,
T. K.
Kim
,
C.
Cacho
,
M.
Horio
,
M.
Ishikado
,
H. M.
Rønnow
,
J.
Chang
Diamond Proposal Number(s):
[32147]
Open Access
Abstract: Strong electron correlations drive Mott insulator transitions. Yet, there exists no framework to classify Mott insulators by their degree of correlation. Cuprate superconductors, with their tunable doping and rich phase diagrams, offer a unique platform to investigate the evolution of these interactions. However, spectroscopic access to a clean half-filled Mott-insulating state is lacking in compounds with the highest superconducting onset temperature. To fill this gap, we introduce a pristine, half-filled thallium-based cuprate system, Tl2Ba5Cu4Ox. Using high-resolution resonant inelastic x-ray scattering, we probe long-lived magnon excitations and uncover a pronounced kink in the magnon dispersion, marked by a simultaneous change in group velocity and lifetime broadening. Modeling the dispersion within a Hubbard-Heisenberg approach, we extract the interaction strength and compare it with other cuprate systems. Our results establish a cuprate universal relation between electron-electron interaction and magnon zone-boundary dispersion. Superconductivity seems to be optimal at intermediate correlation strength, suggesting an optimal balance between localization and itinerancy.
|
Dec 2025
|
|
I12-JEEP: Joint Engineering, Environmental and Processing
|
Diamond Proposal Number(s):
[30411, 33585, 33592]
Open Access
Abstract: Metastable β Ti alloys have potential for vibration damping and actuation applications within the aerospace industry due to thermal and mechanical hysteresis. However, variations in transformation parameters, which are also seen to change following thermal or mechanical cycling, significantly limit industrial acceptance. There is a widespread belief that these variations are a consequence of ⍵ phase formation. However, here we provide evidence to show that this is not necessarily the case. Instead, we show how residual stresses and defect structures are crucial to the transformation of these alloys and present an understanding of the mechanism that governs their behaviour. Importantly, we highlight the consequences for the design of new transforming alloys and component geometries, and how current design theories may need to be employed in conjunction with other methods to effectively prevent longer-term changes in behaviour. To this end, we demonstrate how functional properties could be periodically recovered by introducing short intercycle heat treatments and suggest possible next steps for advancing our understanding of these materials.
|
Nov 2025
|
|
I05-ARPES
|
Jiabao
Yang
,
Mihir
Date
,
Irián Sánchez
Ramírez
,
Vicky
Hasse
,
Deepnarayan
Biswas
,
Stuart S. P.
Parkin
,
Maia G.
Vergniory
,
Fernando
De Juan
,
Claudia
Felser
,
Matthew D.
Watson
,
Niels B. M.
Schroeter
Diamond Proposal Number(s):
[33319]
Open Access
Abstract: Recent work suggests that crystal structures with two sublattice pairs per primitive cell can host “dark states”, electronic states that barely interact with light due to destructive interference, which makes them invisible in photoemission. In practice, however, dark states are only approximately dark, arising from near but imperfect translation symmetries. Here, we demonstrate a practical consequence of this in the semiconductor (NbSe4)3I: Although its band structure indicates an almost direct gap, the material behaves optically like an indirect-gap semiconductor. Angle-resolved photoemission spectroscopy uncovers weak spectral-weight bands folded from a larger Brillouin zone, reflecting approximate intra-unit-cell symmetry. These states form a small direct band gap consistent with transport data but exhibit very low optical transition probability. Instead, optical absorption is dominated by higher-energy transitions involving bands with stronger spectral weight, effectively enlarging the observed optical gap. Our results show that dark states are approximate phenomena with significant consequences for optoelectronic properties.
|
Nov 2025
|
|
I15-Extreme Conditions
|
Diamond Proposal Number(s):
[34535]
Open Access
Abstract: Transition metals, including Iridium, are crucial for understanding planetary cores and developing critical technologies due to their unique properties under extreme high-pressure and high-temperature conditions. Although Ir’s room-temperature phase remains stable, its pressure-temperature phase diagram is largely unknown, with only a single experimental melting point reported previously. A notable gap in knowledge is the lack of experimental evidence for solid-solid phase transitions predicted by theoretical models. Here we show a new investigation into the phase diagram of iridium, employing a combination of resistive-heated and laser-heated diamond anvil cells coupled with synchrotron X-ray diffraction. Our findings confirm that Ir maintains its face-centered cubic structure up to 101 GPa and 5600 K. We determined five new melting points that corroborate computational predictions, providing a more robust foundation for the melting curve. The resulting thermal equation of state offers a definitive dataset that can serve as a reliable pressure standard and advance the design of technologies using Ir.
|
Oct 2025
|
|
I06-Nanoscience (XPEEM)
|
Vincent
Polewczyk
,
Alexander Yu
Petrovic
,
Brice
Sarpi
,
Dirk
Backes
,
Hebatalla
Elnaggar
,
Payal
Wadhwa
,
Alessio
Filippetti
,
Giorgio
Rossi
,
Piero
Torelli
,
Giovanni
Vinai
,
Francesco
Maccherozzi
,
Bruce A.
Davidson
Diamond Proposal Number(s):
[11678]
Open Access
Abstract: In the growing field of spintronic devices incorporating antiferromagnetic materials, control of the domain configuration and Néel axis orientation is critical for technological implementations. Here we show by X-ray magnetic linear dichroism in photoelectron emission microscopy how antiferromagnetic properties of LaFeO3 (LFO) thin films can be tailored through epitaxial strain. LFO films were grown via molecular beam epitaxy with precise stoichiometric control, using substrates that span a range of strain states—from compressive to tensile—and crystal symmetries, including different crystallographic orientations. First, we show that epitaxial strain dictates the Néel axis orientation, shifting it from completely in-plane under compressive strain to completely out-of-plane under tensile strain, regardless of the substrate crystal symmetry. Second, we find that LFO films grown on cubic substrates exhibit a fourfold distribution of antiferromagnetic domains, but can be controlled by varying the substrate miscut, while those on orthorhombic substrates, regardless of strain state, form large-scale monodomains, a highly desirable feature for spintronic applications.
|
Jul 2025
|
|
I05-ARPES
|
Diamond Proposal Number(s):
[33694, 34335]
Open Access
Abstract: Stacking of strongly-correlated 2D materials is opening the possibility to demonstrate novel electronic or magnetic ordering phenomena. In this regard the intrinsic polytypism of tantalum dichalcogenides has emerged as a platform to generate clean and controllable material interfaces. Here, we report on the Fermi surface of 4Hb-TaSe2, a polytype which consists of alternately stacked layers with octahedral (T) and trigonal prismatic (H) coordination of tantalum in the Se-Ta-Se layers. The material is known to host a charge density wave (CDW) phase with star clusters in the T-layers, intercalated by metallic H-layers, but its momentum resolved electronic structure remains undetermined. Using selective area angle resolved photoemission spectroscopy on the T termination combined with ab initio calculations, we unveil a finely structured Fermi surface arising from band folding in the reconstructed Brillouin zone caused by the CDW star clusters. The star-shaped Fermi surface is rotated away from the high-symmetry directions of the normal phase, and exhibits pseudochirality. Theoretical analysis supports the metallic nature of the system and interlayer interactions leading to hybridization. The work provides a detailed overview on the impact of band hybridization with the CDW on the Fermi surface of a material for new phases of quantum matter.
|
Feb 2025
|
|
I16-Materials and Magnetism
|
Diamond Proposal Number(s):
[34302]
Open Access
Abstract: Multiferroic materials can host a plethora of intriguing phenomena due to the presence of multiple ferroic properties that break both spatial inversion symmetry and time reversal symmetry at an observable scale. Hexagonal manganite multiferroics are of particular interest as the properties of their symmetry-lowering phase transition can be described by a Mexican-hat-like potential energy surface. The early universe is proposed to have undergone a symmetry-lowering phase transition that is described by a similar Mexican-hat-like potential that gives rise to the formation of one-dimensional topologically protected defects known as cosmic strings. According to the Kibble-Zurek mechanism, hexagonal manganite multiferroics can host the crystallographic equivalent of cosmic strings and can therefore serve as a testing ground for exploration of concepts in cosmology. To date, however, direct imaging of 1D topological defects in a condensed matter material system has not been achieved. Here we report on robust three-dimensional imaging of topologically protected strings in a single hexagonal manganite nanocrystal, enabled by advances in experimental techniques. Our findings reveal multiferroic strings with a preferred phase vortex winding direction and average separation of ~93 nm.
|
Jan 2025
|
|
B18-Core EXAFS
I11-High Resolution Powder Diffraction
|
Lutong
Shan
,
Yujie
Ma
,
Shaojun
Xu
,
Meng
Zhou
,
Meng
He
,
Alena M.
Sheveleva
,
Rongsheng
Cai
,
Daniel
Lee
,
Yongqiang
Chen
,
Boya
Tang
,
Bing
Han
,
Yinlin
Chen
,
Lan
An
,
Tianze
Zhou
,
Martin
Wilding
,
Alexander S.
Eggeman
,
Floriana
Tuna
,
Eric J. L.
Mcinnes
,
Sarah J.
Day
,
Stephen P.
Thompson
,
Sarah J.
Haigh
,
Xinchen
Kang
,
Buxing
Han
,
Martin
Schroeder
,
Sihai
Yang
Diamond Proposal Number(s):
[33115, 31729]
Open Access
Abstract: The design and preparation of efficient catalysts for ammonia production under mild conditions is a desirable but highly challenging target. Here, we report a series of single-atom catalysts [M-SACs, M = Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Mo(II)] derived from UiO-66 containing structural defects and their application to electrochemical reduction of nitrate (NO3-) to ammonia (NH3). Cu-SAC and Fe-SAC exhibit remarkable yield rates for NH3 production of 30.0 and 29.0 mg h−1 cm−2, respectively, with a high Faradaic efficiency (FENH3) of over 96% at −1.0 V versus the reversible hydrogen electrode. Importantly, their catalytic performance can be retained in various simulated wastewaters. Complementary experiments confirmed the nature of single-atom sites within these catalysts and the binding domains of NO3- in UiO-66-Cu. In situ spectroscopic techniques, coupled with density functional theory calculations confirm the strong binding of NO3- and the formation of reaction intermediates, thus facilitating the catalytic conversion to NH3.
|
Jun 2024
|
|
