I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[36775, 26668]
Open Access
Abstract: A variable-temperature and pressure single-crystal diffraction study of hybrid improper ferroelectric Sr3Sn2O7 is reported. In combination with symmetry analysis, we reveal that the application of pressure and temperature induce distinct phase transition pathways, driven by a differing response of the octahedral rotations to these stimuli. Contrary to what has been previously predicted, we observe the ferroelectric to paraelectric phase transition between 10.17(18) and 12.13(14) GPa, meaning the hybrid improper ferroelectric phase remains stable to significantly higher pressures than expected.
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Jun 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25166]
Open Access
Abstract: We report two three-dimensional metal-organic frameworks constructed from Fe3+ and the ligand, 2,5-furandicarboxylate (FDC) that can be derived from biomass. One contains an unprecedented infinite-rod-shaped building unit, and the other is the first crystalline framework of FDC that contains solely iron in the metal nodes. The materials are formed as microcrystals and their structures determined using 3D-electron diffraction with the bulk confirmed by powder XRD. UOW-7, NaFe5O3(FDC)4(CH3COO)2 is a bimetallic structure with acetate as co-ligand, constructed from infinite chains of iron octahedra, wherein tetramers comprising edge-sharing pairs linked by corner sharing octahedra are crosslinked by FDC ligands. In contrast, UOW-8, Fe2O(FDC)2(H2O)2]·(H2O)4 contains a rare form of tetrameric building unit, cross-linked by FDC, and having Fe-bound water as well as occluded water. The materials crystallise under hydrothermal conditions and are water-stable coordination polymers with no measurable free pore space. The catalytic ability of UOW-7 and UOW-8 is, nevertheless, established in the reduction of 4-nitrophenol to 4-aminophenol by borohydride, where both act as recyclable, catalysts to give ~100% yield of the product without use of precious metals. UOW-8 is found to have the more favourable reaction kinetics, likely due to the presence of surface Lewis acidic Fe3+ centres that enhance substrate binding.
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Mar 2025
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I11-High Resolution Powder Diffraction
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S.
Vaidya
,
A.
Hernández-Melián
,
J. P.
Tidey
,
S. P. M.
Curley
,
S.
Sharma
,
P.
Manuel
,
C.
Wang
,
G. L.
Hannaford
,
S. J.
Blundell
,
Z. E.
Manson
,
J. L.
Manson
,
J.
Singleton
,
T.
Lancaster
,
R. D.
Johnson
,
P. A.
Goddard
Open Access
Abstract: We investigate the magnetic properties of 𝑆=1 antiferromagnetic diamond-lattice, Ni𝑋2(pyrimidine)2 (𝑋=Cl, Br), hosting a single-ion anisotropy (SIA) orientation which alternates between neighboring sites. Through neutron diffraction measurements of the 𝑋=Cl compound, the ordered state spins are found to align collinearly along a pseduo-easy axis, a unique direction created by the intersection of two easy planes. Similarities in the magnetization, exhibiting spin-flop transitions, and the magnetic susceptibility in the two compounds imply that the same magnetic structure and a pseduo-easy axis is also present for 𝑋=Br. We estimate the Hamiltonian parameters by combining analytical calculations and Monte Carlo (MC) simulations of the spin-flop and saturation field. The MC simulations also reveal that the spin-flop transition occurs when the applied field is parallel to the pseduo-easy axis. Contrary to conventional easy-axis systems, there exist field directions perpendicular to the pseduo-easy axis for which the magnetic saturation is approached asymptotically and no symmetry-breaking phase transition is observed at finite fields.
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Nov 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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I11-High Resolution Powder Diffraction
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Struan
Simpson
,
Cameron A. M.
Scott
,
Fernando
Pomiro
,
Jeremiah P.
Tidey
,
Urmimala
Dey
,
Fabio
Orlandi
,
Pascal
Manuel
,
Martin R.
Lees
,
Zih-Mei
Hong
,
Wei-Tin
Chen
,
Nicholas C.
Bristowe
,
Mark S.
Senn
Diamond Proposal Number(s):
[32893]
Open Access
Abstract: Magnetoelectric multiferroics hold great promise for the development of new sustainable memory devices. However, practical applications of many existing multiferroic materials are infeasible due to the weak nature of the coupling between the magnetic and electrical orderings, meaning new magnetoelectric multiferroics featuring intrinsic coupling between their component orderings are sought instead. Here, we apply a symmetry-informed design approach to identify and realize the new manganite perovskite CeBaMn2O6 in which magnetoelectric coupling can be achieved via an intermediary non-polar structural distortion. Through first-principles calculations, we demonstrate that our chosen prototype system contains the required ingredients to achieve the desired magnetoelectric coupling. Using high-pressure/high-temperature synthesis conditions, we have been able to synthesize the CeBaMn2O6 perovskite system for the first time. Our subsequent neutron and electron diffraction measurements reveal that the desired symmetry-breaking ingredients exist in this system on a nanoscopic length scale, enabling magnetoelectric nanoregions to emerge within the material. Through this work, we showcase the potential of the new CeBaMn2O6 perovskite material as a promising system in which to realize strong magnetoelectric coupling, highlighting the potential of our symmetry-informed design approach in the pursuit of new magnetoelectric multiferroics for next-generation memory devices.
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Aug 2024
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[25166]
Open Access
Abstract: The tetragonal tungsten bronze, Sr2NaNb5O15, shows promise for application in high-temperature high-efficiency capacitors vital for the sustainable energy revolution. Previously, the structural complexity of this and related materials has obscured the mechanisms underpinning two large anomalies in relative permittivity (εr) which give rise to their exceptionally broad dielectric response. Here, we comprehensively investigate the structural evolution from −173 to 627 °C, combining electron, X-ray and neutron diffraction, electron microscopy, and first principles electronic structure calculations to unambiguously identify the structural origins of both anomalies. The peak in εr at 305 °C is associated with a polar-nonpolar phase transition, wherein cations displace along the c axis. Guided by DFT, we identify a further transition upon cooling, associated with the second peak at −14 °C, linked to the softening of an in-plane polar distortion with a correlation length limited by ferroelastic nano-domains arising from rigid-unit-like tilting of NbO6 octahedra at high temperature, imparting relaxor-like behaviour. Thus, the two dielectric anomalies in Sr2NaNb5O15 are associated with two distinct crystallographic phase transitions and their interplay with a microstructure that arises from a third, non-polar structural distortion. Chemical control of these will enable development of tuneable materials with dielectric properties suitable for high-temperature energy storage applications.
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May 2024
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[26668]
Open Access
Abstract: The crystal structures of four coordination polymers constructed from Sn(II) and polydentate carboxylate ligands are reported. All are prepared under hydrothermal conditions in KOH or LiOH solutions (either water or methanol–water) at 130−180 °C and crystallize as small crystals, microns or less in size. Single-crystal structure solution and refinement are performed using synchrotron X-ray diffraction for two materials and using 3D electron diffraction (3DED) for the others. Sn2(1,3,5-BTC)(OH), where 1,3,5-BTC is benzene-1,3,5-tricarboxylate, is a new polymorph of this composition and has a three-dimensionally connected structure with potential for porosity. Sn(H-1,3,5-BTC) retains a partially protonated ligand and has a 1D chain structure bound by hydrogen bonding via ─COOH groups. Sn(H-1,2,4-BTC) contains an isomeric ligand, benzene-1,2,4-tricarboxylate, and contains inorganic chains in a layered structure held by hydrogen bonding. Sn2(DOBDC), where DOBDC is 2,5-dioxido-benzene-1,4-dicarboxylate, is a new polymorph for this composition and has a three-dimensionally connected structure where both carboxylate and oxido groups bind to the tin centers to create a dense network with dimers of tin. In all materials, the Sn centers are found in highly asymmetric coordination, as expected for Sn(II). For all materials phase purity of the bulk is confirmed using powder X-ray diffraction, thermogravimetric analysis, and infrared spectroscopy.
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Mar 2024
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I19-Small Molecule Single Crystal Diffraction
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Jeremiah P.
Tidey
,
En-Pei
Liu
,
Yen-Chung
Lai
,
Yu-Chun
Chuang
,
Wei-Tin
Chen
,
Lauren J.
Cane
,
Chris
Lester
,
Alexander N. D.
Petsch
,
Anna
Herlihy
,
Arkadiy
Simonov
,
Stephen M.
Hayden
,
Mark
Senn
Diamond Proposal Number(s):
[27647]
Open Access
Abstract: Definitive understanding of superconductivity and its interplay with structural symmetry in the hole-doped lanthanum cuprates remains elusive. The suppression of superconductivity around 1/8th doping maintains particular focus, often attributed to charge-density waves (CDWs) ordering in the low-temperature tetragonal (LTT) phase. Central to many investigations into this interplay is the thesis that La1.875Ba0.125CuO4 and particularly La1.675Eu0.2Sr0.125CuO4 present model systems of purely LTT structure at low temperature. However, combining single-crystal and high-resolution powder X-ray diffraction, we find these to exhibit significant, intrinsic coexistence of LTT and low-temperature orthorhombic domains, typically associated with superconductivity, even at 10 K. Our two-phase models reveal substantially greater tilting of CuO6 octahedra in the LTT phase, markedly buckling the CuO2 planes. This would couple significantly to band narrowing, potentially indicating a picture of electronically driven phase segregation, reminiscent of optimally doped manganites. These results call for reassessment of many experiments seeking to elucidate structural and electronic interplay at 1/8 doping.
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Aug 2022
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I15-Extreme Conditions
I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[1022, 1216, 3031, 6409, 7532]
Abstract: The application of pressures of up to about 10 GPa may induce significant geometric, configurational, conformational and packing changes in molecular solids. This review highlights and describes recent advances in high pressure studies of coordination complexes, many of which have been conducted at synchrotrons or other central facilities. The main focus is on the wide range of geometric changes which occur with pressure. In some cases these changes have associated physical effects, and the review describes materials exhibiting negative linear compressibility, spin cross-over phenomena, magnetism and molecular conduction, as well as detailing the exciting possibilities for future developments in this area of research.
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Oct 2014
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I19-Small Molecule Single Crystal Diffraction
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Dave
Allan
,
Daniel
Bailey
,
Nigel
Bird
,
Alexander J.
Blake
,
Neil R.
Champness
,
Deguang
Huang
,
Conal P.
Keane
,
Jonathan
Mcmaster
,
Tim
Prior
,
Jeremiah
Tidey
,
Martin
Schröder
Diamond Proposal Number(s):
[1022, 1216, 3031, 6409, 7532]
Abstract: The mononuclear macrocyclic Pd-II complex cis[PdCl2([9]aneS(3))]([9]aneS(3) = 1,4,7-trithiacyclo-nonane) converts at 44 kbar into an intensely coloured chain polymer exhibiting distorted octahedral coordination at the metal centre and an unprecedented [1233] conformation for the thioether ligand. The evolution of an intramolecular axial sulfur-metal interaction and an intermolecular equatorial sulfur-metal interaction is central to these changes. High-pressure crystallographic experiments have also been undertaken on the related complexes [PtCl2([9]aneS(3))], [PdBr2([9]aneS(3))], [PtBr2([9]aneS(3))], [PdI2([9]aneS(3))] and [PtI2([9]aneS(3))] in order to establish the effects of changing the halide ligands and the metal centre on the behaviour of these complexes under pressure. While all complexes undergo contraction of the various interaction distances with increasing pressure, only [PdCl2([9]aneS(3))] undergoes a phase change. Pressure-induced I center dot center dot center dot I interactions were observed for [PdI2([9]aneS(3))] and [PtI2([9]aneS(3))] at 19 kbar, but the corresponding Br center dot center dot center dot Br interactions in [PdBr2([9]aneS(3))] and [PtBr2([9]aneS(3))] only become significant at much higher pressure (58 kbar). Accompanying density functional theory (DFT) calculations have yielded interaction energies and bond orders for the sulfur-metal interactions.
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Jun 2014
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