I15-1-X-ray Pair Distribution Function (XPDF)
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Adam F.
Sapnik
,
Philip A.
Chater
,
Dean S.
Keeble
,
John S. O.
Evans
,
Federica
Bertolotti
,
Antonietta
Guagliardi
,
Lise J.
Støckler
,
Elodie A.
Harbourne
,
Anders B.
Borup
,
Rebecca S.
Silberg
,
Adrien
Descamps
,
Clemens
Prescher
,
Benjamin D.
Klee
,
Axel
Phelipeau
,
Imran
Ullah
,
Kárel G.
Medina
,
Tobias A.
Bird
,
Viktoria
Kaznelson
,
William
Lynn
,
Andrew L.
Goodwin
,
Bo B.
Iversen
,
Celine
Crepisson
,
Emil S.
Bozin
,
Kirsten M. Ø.
Jensen
,
Emma E.
Mcbride
,
Reinhard B.
Neder
,
Ian
Robinson
,
Justin S.
Wark
,
Michał
Andrzejewski
,
Ulrike
Boesenberg
,
Erik
Brambrink
,
Carolina
Camarda
,
Valerio
Cerantola
,
Sebastian
Goede
,
Hauke
Höppner
,
Oliver S.
Humphries
,
Zuzana
Konopkova
,
Naresh
Kujala
,
Thomas
Michelat
,
Motoaki
Nakatsutsumi
,
Alexander
Pelka
,
Thomas R.
Preston
,
Lisa
Randolph
,
Michael
Roeper
,
Andreas
Schmidt
,
Cornelius
Strohm
,
Minxue
Tang
,
Peter
Talkovski
,
Ulf
Zastrau
,
Karen
Appel
,
David A.
Keen
Diamond Proposal Number(s):
[39017]
Open Access
Abstract: High-quality total scattering data, a key tool for understanding atomic-scale structure in disordered materials, require stable instrumentation and access to high momentum transfers. This is now routine at dedicated synchrotron instrumentation using high-energy X-ray beams, but it is very challenging to measure a total scattering dataset in less than a few microseconds. This limits their effectiveness for capturing structural changes that occur at the much faster timescales of atomic motion. Current X-ray free-electron lasers (XFELs) provide femtosecond-pulsed X-ray beams with maximum energies of ∼24 keV, giving the potential to measure total scattering and the attendant pair distribution functions (PDFs) on femtosecond timescales. We demonstrate that this potential has been realized using the HED scientific instrument at the European XFEL and present normalized total scattering data for 0.35 Å−1 < Q < 16.6 Å−1 and their PDFs from a broad spectrum of materials, including crystalline, nanocrystalline and amorphous solids, liquids and clusters in solution. We analyzed the data using a variety of methods, including Rietveld refinement, small-box PDF refinement, joint reciprocal–real-space refinement, cluster refinement and Debye scattering analysis. The resolution function of the setup is also characterized. We conclusively show that high-quality data can be obtained from a single ∼30 fs XFEL pulse for multiple different sample types. Our efforts not only significantly increase the existing maximum reported Q range for an S(Q) measured at an XFEL but also mean that XFELs are now a viable X-ray source for the broad community of people using reciprocal-space total scattering and PDF methods in their research.
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Sep 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[32893]
Open Access
Abstract: The average structure of the solid solution LaMn1−𝑥Ga𝑥O3 (LMGO) has been investigated from a symmetry-motivated approach utilizing synchrotron x-ray and neutron powder diffraction techniques. We show experimentally that a trilinear coupling term (Γ+
5M+
2M+
3) between shear strain, octahedral rotation, and the 𝐶-type orbital ordering mode is responsible for driving the orthorhombic to pseudocubic phase transition occurring in the composition range 0.5<𝑥<0.6. Our Monte Carlo simulations elucidate the macroscopic origin of this coupling to shear strain, and point to its importance with respect to controlling the orbital order-disorder transitions. We find that the emergence of the pseudocubic state can be rationalized by considering the competition between this trilinear term and a linear-quadratic term of the out-of-phase octahedral tilting with strain (Γ+
5(R−
5)2). Illustrating the general nature of these results, we construct a simple function that captures the change in Landau free energy at the order-disorder transition, in parameters that are trivial to relate to the concentration of Jahn-Teller active species, temperature, tolerance factor, and unit cell strain, for a broad range of manganite perovskites. Our results point to the fact that far from the pseudocubic state being a symptom of orbital disorder, in many cases, it is more correctly to view it as a cause. The results have a broad impact on the study of orbital ordering physics in the perovskite materials and on chemical and physical control parameters through which to tune the richness of the intertwined physical properties.
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Sep 2025
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[9610, 12763, 9019, 32893, 11574]
Open Access
Abstract: Iron-based superconductors have attracted much attention for their high superconducting temperatures and high upper critical fields, which make them promising candidates for application as well as fundamentally important for our understanding of superconductivity. One feature of these superconductors is their ability to intercalate and deintercalate species from between their iron-containing layers, something not available in cuprate high-temperature superconductors or niobium-based conventional superconductors used in technologies. This provides an opportunity for switchable changes in the superconducting properties as a function of chemical conditions, but the resulting structures are often hard to characterize due to loss of crystallinity and sometimes the formation of multiphase products. Here, we explore both the synthesis and decomposition of potassium and ammonia-intercalated iron selenide superconductors through in situ powder X-ray diffraction. We report a complete phase diagram including two new solution-stable ammonia-rich phases and several metastable forms. We give accurate characterization of the reported ammonia-poor forms using a combination of neutron and X-ray powder diffraction, using an innovative supercell approach to describe the phase breadth within the samples. These results give rare insight into stepwise changes occurring in solids along multiple reaction pathways, which demonstrate the importance of in situ diffraction techniques.
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May 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25166]
Open Access
Abstract: The peritectic compound Li4(OH)3Br has been suggested as a candidate material for latent heat thermal energy storage (TES), due to its high calculated melting enthalpy (804 J g–1) around 300 °C, however experimental reports have obtained much lower values (≤250 J g–1). In this work, we show that the crystal structure established for Li4(OH)3Br in literature corresponds to a metastable hydrated compound, and instead propose that the thermodynamically stable phase belongs to the Pmnm space group. The hydrated phase dehydrates at ∼175 °C, rendering the exceptional previous predictions inapplicable. An experimentally measured melting enthalpy of 263 ± 3 J g–1 is found for high-purity Li4(OH)3Br. Theoretical modeling is used to suggest a crystal structure for Li4(OH)3Br, from which a melting enthalpy of 260 J g–1 is calculated, in good agreement with the experimental work, and supporting that nonetheless impressive storage capacity at ∼290 °C can be offered by Li4(OH)3Br.
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Apr 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25166]
Open Access
Abstract: In this paper, we build on previous work to characterize a phase with stoichiometry Li3(OH)2Br existing between ∼225 and ∼275 °C in the LiBr-LiOH phase diagram. Diffraction studies indicate that the phase takes a hexagonal unit cell, and theoretical modeling is used to suggest a possible crystal structure. Nuclear magnetic resonance spectroscopy and electrochemical impedance spectroscopy measurements demonstrate excellent lithium-ion dynamics in this phase, with an ionic conductivity of 0.12 S cm–1 at 250 °C. Initial attempts to stabilize this phase at room temperature through quenching were not successful. Instead, a metastable state demonstrating poor ionic conductivity is found to form. This is an important consideration for the synthesis of Li2OHBr solid-state electrolytes (also found in the LiBr-LiOH phase diagram) which are synthesized by cooling through phase fields containing Li3(OH)2Br, and are hence susceptible to these impurities.
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Apr 2025
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I11-High Resolution Powder Diffraction
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Liam A. V.
Nagle-Cocco
,
Annalena R.
Genreith-Schriever
,
James M. A.
Steele
,
Camilla
Tacconis
,
Joshua D.
Bocarsly
,
Olivier
Mathon
,
Joerg C.
Neuefeind
,
Jue
Liu
,
Christopher A.
O’keefe
,
Andrew L.
Goodwin
,
Clare P.
Grey
,
John S. O.
Evans
,
Sian E.
Dutton
Diamond Proposal Number(s):
[34243, 28349]
Open Access
Abstract: Below its Jahn–Teller transition temperature, TJT, NaNiO2 has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO6 and Jahn–Teller-distorted NiO6 octahedra. Above TJT where NaNiO2 is rhombohedral, diffraction measurements show the absence of a cooperative Jahn–Teller distortion, accompanied by an increase in the unit cell volume. Using neutron total scattering, solid-state Nuclear Magnetic Resonance (NMR), and extended X-ray absorption fine structure (EXAFS) experiments as local probes of the structure we find direct evidence for a displacive, as opposed to order–disorder, Jahn–Teller transition at TJT. This is supported by ab initio molecular dynamics (AIMD) simulations. To our knowledge this study is the first to show a displacive Jahn–Teller transition in any material using direct observations with local probe techniques.
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Oct 2024
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[34953]
Open Access
Abstract: We use in situ synchrotron X-ray diffraction measurements to monitor the solvothermal crystallization mechanism of the aperiodic metal–organic framework TRUMOF-1. Following an initial incubation period, TRUMOF-1 forms as a metastable intermediate that subsequently transforms into an ordered product with triclinic crystal symmetry. We determine the structure of this ordered phase, which we call msw-TRUMOF-1, and show that it is related to TRUMOF-1 through topotactic reorganization of linker occupancies. Our results imply that the connectivity of TRUMOF-1 can be reorganized, as required for data storage and manipulation applications.
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Sep 2024
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25166]
Open Access
Abstract: Potassium-ion batteries (KIBs) are emerging as a promising alternative technology to lithium-ion batteries (LIBs) due to their significantly reduced dependency on critical minerals. KIBs may also present an opportunity for superior fast-charging compared to LIBs, with significantly faster K-ion electrolyte transport properties already demonstrated. In the absence of a viable K-ion electrolyte, a full-cell KIB rate model in commercial cell formats is required to determine the fast-charging potential for KIBs. However, a thorough and accurate characterisation of the critical electrode material properties determining rate performance—the solid state diffusivity and exchange current density—has not yet been conducted for the leading KIB electrode materials. Here, we accurately characterise the effective solid state diffusivities and exchange current densities of the graphite negative electrode and potassium manganese hexacyanoferrate
(KMF) positive electrode, through a combination of optimised material design and state-of-the-art analysis. Finally, we present a Doyle-Fuller-Newman model of a KIB full cell with realistic geometry and loadings, identifying the critical materials properties that limit their rate capability.
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Aug 2024
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[31498]
Open Access
Abstract: By virtue of their open network structures and low densities, metal–organic frameworks (MOFs) are soft materials that exhibit elastic instabilities at low applied stresses. The conventional strategy for improving elastic stability is to increase the connectivity of the underlying MOF network, which necessarily increases the material density and reduces the porosity. Here we demonstrate an alternative paradigm, whereby elastic stability is enhanced in a MOF with an aperiodic network topology. We use a combination of variable-pressure single-crystal X-ray diffraction measurements and coarse-grained lattice-dynamical calculations to interrogate the high-pressure behaviour of the topologically aperiodic system TRUMOF-1, which we compare against that of its ordered congener MOF-5. We show that the topology of the former quenches the elastic instability responsible for pressure-induced framework collapse in the latter, much as irregularity in the shapes and sizes of stones acts to prevent cooperative mechanical failure in drystone walls. Our results establish aperiodicity as a counter-intuitive design motif in engineering the mechanical properties of framework structures that is relevant to MOFs and larger-scale architectures alike.
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Jul 2024
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[26330]
Open Access
Abstract: We use a combination of X-ray pair distribution function (PDF) measurements, lattice dynamical calculations, and ab initio density functional theory (DFT) calculations to study the local structure and dynamics in various MPt(CN)6 Prussian blue analogues. In order to link directly the local distortions captured by the PDF with the lattice dynamics of this family, we develop and apply a new “interaction-space” PDF refinement approach. This approach yields effective harmonic force constants, from which the (experiment-derived) low-energy phonon dispersion relations can be approximated. Calculation of the corresponding Grüneisen parameters allows us to identify the key modes responsible for negative thermal expansion (NTE) as arising from correlated tilts of coordination octahedra. We compare our results against the phonon dispersion relations determined using DFT calculations, which identify the same NTE mechanism.
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May 2024
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