I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[37504]
Open Access
Abstract: Crystalline hybrid organic–inorganic structures from the coordination polymer (CP)/metal–organic framework (MOF) family have recently emerged as materials which liquify upon heating to high temperature and then transform into glass upon cooling to room temperature. This melt-quench process of this material family generally requires an anaerobic atmosphere to avoid oxidation of organic component at high temperature. Anaerobicity here brings in an extra cost and makes melt-quench setup robust. Besides, these hybrid liquids often show intriguing thermal behaviour such as exothermic recrystallization (on cooling), cold crystallization (on reheating), etc. which again limits the typical melt-quench process of glass fabrication and processability. Here we turn to hybrid organic–inorganic structures of one-dimensional (1-D) family and design five 1-D (PrPh3P)2[M(dca)4] (PrPh3P = propyltriphenylphosphonium; M = Mn, Fe, Co, Ni, Cu; dca = dicyanamide) compounds which overcome above hurdles and were successfully vitrified upon direct in-situ melt-quenching on laboratory time scales under aerobic conditions. The combined spectroscopic and X-ray total scattering studies reveal successful structural characterization of these glasses that largely retain the coordination bonding of the crystalline phase and show valuable physical properties such as low liquid fragility (m), large ‘glass-crystal network density deficit’ (Δρ/ρg)network, high glass-forming ability (GFA) and polymer-like mechanical hardness (H).
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Mar 2026
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[39102]
Abstract: The Na3PnS4 (Pn = P, Sb) solid electrolytes are promising candidates for sodium solid-state batteries due to their potential high ionic conductivities. Structural modifications of these materials can induce a tetragonal-to-cubic phase transition, either by increasing temperature or by aliovalent substitutions. In this study, we introduce pressure as an alternative approach to observe the tetragonal-to-cubic phase transition in these materials. In situ synchrotron high-pressure powder X-ray diffraction shows a tetragonal-to-cubic phase transition at pressures of 2.9 GPa for Na3SbS4 and 14.6 GPa for Na3PS4. Rietveld refinements and symmetry analysis provide insights into the displacive phase transition mechanism related to the motion of Na+ and the rotation of the SbS43– tetrahedra. Density functional theory calculations confirm that the cubic phase becomes thermodynamically favorable under high pressure compared to the tetragonal phase. These findings highlight the importance of high-pressure considerations in tailoring the properties of ionic conductors, an area that remains underexplored.
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Jun 2025
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I15-1-X-ray Pair Distribution Function (XPDF)
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Bikash Kumar
Shaw
,
Lucia
Corti
,
Joshua M.
Tuffnell
,
Celia
Castillo-Blas
,
Patrick
Schlachta
,
Georgina P.
Robertson
,
Lauren
Mchugh
,
Adam F.
Sapnik
,
Sebastian A.
Hallweger
,
Philip A.
Chater
,
Gregor
Kieslich
,
David A.
Keen
,
Sian E.
Dutton
,
Frédéric
Blanc
,
Thomas D.
Bennett
Diamond Proposal Number(s):
[20038]
Open Access
Abstract: ABX3-type hybrid organic–inorganic structures have recently emerged as a new class of meltable materials. Here, by the use of phenylphosphonium derivatives as A cation, we study liquid- and glass-forming behavior of a new family of hybrid structures, (RPh3P)[Mn(dca)3] (R = Me, Et, Ph; dca = dicyanamide). These new compounds melt at 196–237 °C (Tm) and then vitrify upon cooling to room temperature, forming glasses. In situ glass formation of this new family of materials was probed on a large scale using a variable-temperature PXRD experiment. Structure analyses of the crystalline and the glasses were carried out by solid-state nuclear magnetic resonance spectroscopy and synchrotron X-ray total scattering techniques for using the pair distribution function. The mechanical properties of the glasses produced were evaluated showing promising durability. Thermal and electrical conductivities showed low thermal conductivities (κ ∼ 0.07–0.09 W m–1 K–1) and moderate electrical conductivities (σ ∼ 10–4–10–6 S m–1) at room temperature, suggesting that by the precise control of the A cation, we can tune meltable hybrid structures from moderate conductors to efficient thermal insulators. Our results raise attention on the practical use of this new hybrid material in applications including, e.g., photovoltaic devices to prevent light-deposited heat (owing to low κRT), energy harvesting thermoelectric, etc., and advance the structure–property understanding.
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Dec 2024
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[30815]
Open Access
Abstract: Van der Waals (vdW) magnets offer unique opportunities for exploring magnetism in the 2D limit. Metal-organic magnets (MOM) are of particular interest as the functionalisation of organic ligands can control their physical properties. Here, we demonstrate tuning of mechanical and magnetic function of a noncollinear vdW ferromagnet, NiCl2(btd) (btd = 2,1,3-benzothiadiazole), through creating solid-solutions with the oxygen-substituted analogue ligand 2,1,3-benzoxadiazole (bod). We synthesise solid-solutions, NiCl2(btd)1–x(bod)x , up to x = 0.33 above which we find mixtures form, primarily composed of a new 1D coordination polymer NiCl2(bod)2. Magnetometry on this series shows that bod incorporation reduces the coercivity significantly (up to 60%), without significantly altering the ordering temperatures. Our high pressure synchrotron diffraction measurements up to 0.4 GPa demonstrate that the stiffest axis is the b axis, through the Ni-N-(O/S)-N-Ni bonds, and the softest is the interlayer direction. Doping with bod fine-tunes this compressibility, softening the layers, but stiffening the interlayer axis. This demonstrates that substitution of organic ligands in vdW MOMs can be used to realise targetted magnetic and mechanical properties.
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Oct 2024
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[30815]
Open Access
Abstract: Molecular perovskites are important materials in the area of barocalorics, improper ferroelectrics and ferroelastics, where the search for principles that link composition, structure and mechanical properties is a key challenge. Herein, we report the synthesis of a new series of dicyanamide-based molecular perovskites [A]Ni(C2N3)3, where the A-site cation (A+) is a range of alkylated piperidinium cations. We use this new family to explore how A+ cations determine their mechanical response by measuring the bulk modulus (B) – using high-pressure powder X-ray diffraction. Within the series, we find a positive correlation between the network distortions of the pseudocubic [Ni(C2N3)3]− network and B. Furthermore, we show that we can tune framework distortions, and therefore B, by synthesising A-site solid solutions. The applied methodology is a blueprint for linking framework distortions and mechanical properties in network materials and guides us toward principles for designing macroscopic properties via systematic compositional changes in molecular perovskites.
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Jul 2024
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I15-Extreme Conditions
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Silva M.
Kronawitter
,
Richard
Röß-Ohlenroth
,
Sebastian A.
Hallweger
,
Marcel
Hirrle
,
Hans Albrecht
Krug
,
Tobias
Luxenhofer
,
Emily
Myatt
,
Jem
Pitcairn
,
Matthew J.
Cliffe
,
Dominik
Daisenberger
,
Jakub
Wojciechowski
,
Dirk
Volkmer
,
Gregor
Kieslich
Diamond Proposal Number(s):
[30815]
Open Access
Abstract: Fe(II)-containing Metal-Organic Frameworks (MOFs) that exhibit temperature-induced spin-crossover (SCO) are candidate materials in the field of sensing, barocalorics, and data storage. Their responsiveness towards pressure is therefore of practical importance and is related to their longevity and processibility. The impact of Fe(II) spin-state on the pressure responsiveness of MOFs is yet unexplored. Here we report the synthesis of two new Fe(II)-based MOFs, i.e. Fe(cta)2 ((cta)– = 1,4,5,6-tetrahydrocyclopenta[d][1,2,3]triazolate) and Fe(mta)2 ((mta)– = methyl[1,2,3]triazolate), which are both in high-spin at room temperature. Together with the isostructural MOF Fe(ta)2 ((ta)– = [1,2,3]triazolate), which is in its low-spin state at room temperature, we apply these as model systems to show how spin-state controls their mechanical properties. As a proxy, we use their bulk modulus, which was obtained via high-pressure powder X-ray diffraction experiments. We find that an interplay of spin-state, steric effects, void fraction, and absence of available distortion modes dictates their pressure-induced structural distortions. Our results show for the first time the role of spin-state on the pressure-induced structural deformations in MOFs and bring us a step closer to estimating the effect of pressure as a stimulus on MOFs a priori.
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Feb 2024
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I15-Extreme Conditions
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Vasiliki
Faka
,
Matthias T.
Agne
,
Martin A.
Lange
,
Dominik
Daisenberger
,
Björn
Wankmiller
,
Stefan
Schwarzmüller
,
Hubert
Huppertz
,
Oliver
Maus
,
Bianca
Helm
,
Thorben
Boeger
,
Johannes
Hartel
,
Josef Maximilian
Gerdes
,
Jamie J.
Molaison
,
Gregor
Kieslich
,
Michael R.
Hansen
,
Wolfgang G.
Zeier
Diamond Proposal Number(s):
[31791]
Abstract: The influence of the microstructure on the ionic conductivity and cell performance is a topic of broad scientific interest in solid-state batteries. The current understanding is that interfacial decomposition reactions during cycling induce local strain at the interfaces between solid electrolytes and the anode/cathode, as well as within the electrode composites. Characterizing the effects of internal strain on ion transport is particularly important, given the significant local chemomechanical effects caused by volumetric changes of the active materials during cycling. Here, we show the effects of internal strain on the bulk ionic transport of the argyrodite Li6PS5Br. Internal strain is reproducibly induced by applying pressures with values up to 10 GPa. An internal permanent strain is observed in the material, indicating long-range strain fields typical for dislocations. With increasing dislocation densities, an increase in the lithium ionic conductivity can be observed that extends into improved ionic transport in solid-state battery electrode composites. This work shows the potential of strain engineering as an additional approach for tuning ion conductors without changing the composition of the material itself.
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Jan 2024
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I15-Extreme Conditions
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Madeleine
Geers
,
David M.
Jarvis
,
Cheng
Liu
,
Siddharth S.
Saxena
,
Jem
Pitcairn
,
Emily
Myatt
,
Sebastian A.
Hallweger
,
Silva M.
Kronawitter
,
Gregor
Kieslich
,
Sanliang
Ling
,
Andrew B.
Cairns
,
Dominik
Daisenberger
,
Oscar
Fabelo
,
Laura
Cañadillas-Delgado
,
Matthew J.
Cliffe
Diamond Proposal Number(s):
[30815]
Open Access
Abstract: Two-dimensional materials offer a unique range of magnetic, electronic, and mechanical properties which can be controlled by external stimuli. Pressure is a particularly important stimulus, as it can be achieved readily and can produce large responses, especially in low-dimensional materials. In this paper, we explore the pressure dependence of the structural and magnetic properties of a two-dimensional van der Waals (vdW) molecular framework antiferromagnet with ferromagnetic layers,
Ni
(
NCS
)
2
, up to 8.4 kbar. Through a combination of x-ray and neutron diffraction analysis, we find that
Ni
(
NCS
)
2
is significantly more compressible than comparable vdW metal halides, and its response is anisotropic not only out of the plane, but also within the layers. Using bulk magnetization and neutron diffraction data, we show that the ambient layered antiferromagnetic phase is maintained up to the largest investigated pressure, but with an enhanced Néel temperature,
T
N
(
Δ
T
N
/
T
N
=
+
19
%
), and a large pressure sensitivity (
Q
=
1
T
N
d
T
N
d
P
=
+
2.3
%
kbar
−
1
), one of the larger values of magnetic pressure responsiveness for a vdW material. Density functional theory calculations suggest that this is due to increasing three dimensionality. These results provide insights into the pressure response of molecular framework vdW magnets and suggest that the investigation of other molecular framework vdW magnets might uncover contenders for future pressure-switchable devices.
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Oct 2023
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[22477]
Open Access
Abstract: Engineering the interplay of structural degrees of freedom that couple to external stimuli such as temperature and pressure is a powerful approach for material design. New structural degrees of freedom expand the potential of the concept, and coordination polymers as a chemically versatile material platform offer fascinating possibilities to address this challenge. Here, we report a new class of perovskite-like AB2X6 coordination polymers based on a [BX3] − ReO3-type host network ([Mn(C2N3)3] −), in which the spatial orientation of divalent A2+ cations ([R3N(CH2)nNR3]2+) with separated charge centers that bridge adjacent ReO3-cavities is introduced as a new geometric degree of freedom. Herringbone and head-to-tail order pattern of [R3N(CH2)nNR3]2+ cations are obtained by varying the separator length n and, together with distortions of the pseudocubic [BX3] − network, they determine the materials’ stimuli-responsive behavior such as counterintuitive large negative compressibility and uniaxial negative thermal expansion. This new family of coordination polymers highlights the chemists’ capabilities of designing matter on a molecular level to address macroscopic material functionality and underpins the opportunities of the design of structural degrees of freedom as a conceptual framework for rational material synthesis in the future.
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Aug 2022
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[21603]
Open Access
Abstract: The high-pressure behaviour of flexible zeolitic imidazolate frameworks (ZIFs) of the ZIF-62 family with the chemical composition M(im)2-x(bim)x is presented (M2+ = Zn2+, Co2+; im– = imidazolate; bim– = benzimidazolate, 0.02 ≤ x ≤ 0.37). High-pressure powder X-ray diffraction shows that the materials contract reversibly from an open pore (op) to a closed pore (cp) phase under a hydrostatic pressure of up to 4000 bar. Sequentially increasing the bim– fraction (x) reinforces the framework, leading to an increased threshold pressure for the op-to-cp phase transition, while the total volume contraction across the transition decreases. Most importantly, the typical discontinuous op-to-cp transition (first order) changes to an unusual continuous transition (second order) for x ≥ 0.35. This allows finetuning the void volume and the pore size of the material continuously by adjusting the pressure, thus opening new possibilities for MOFs in pressure-switchable devices, membranes, and actuators.
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Feb 2022
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