138 results on '"Goodwin AL"'
Search Results
2. Magnetic structure and exchange interactions in the Heisenberg pyrochlore antiferromagnet Gd₂Pt₂O₇
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Welch, PG, Paddison, JAM, Le, MD, Gardner, JS, Chen, W-T, Wildes, AR, Goodwin, AL, and Stewart, JR
- Abstract
The Heisenberg pyrochlore antiferromagnet Gd₂Pt₂O₇ is one of a series of gadolinium pyrochlore compounds with a variety of B-site cations. Despite the expected simplicity of a spin-onlyGd3+Heisenberg interaction model, the gadolinium pyrochlore series exhibits various complex magnetic ground states at low temperature. Gd₂Pt₂O₇ displays the highest temperature magnetic order of the series withTN=1.6K, which has been attributed to enhanced superexchange pathways facilitated by empty5degPt orbitals. In this study, we use various neutron scattering techniques on an isotopically enriched polycrystalline160Gd₂Pt₂O₇sample to examine the magnetic structure and spin-wave excitation spectrum belowTNin order to extract the dominant exchange interactions. We find that the ground-state magnetic structure is the Palmer-Chalker state previously seen in Gd₂Pt₂O₇ with an associated gapped excitation spectrum consistent with enhanced exchange interactions between further near-neighborGd3+ions. We confirm this exchange model with analysis of the magnetic diffuse scattering in the paramagnetic regime using polarized neutrons.
- Published
- 2022
3. Metal-Organic Nanosheets Formed via Defect-Mediated Transformation of a Hafnium Metal-Organic Framework
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Cliffe, MJ, Castillo-Martínez, E, Wu, Y, Lee, J, Forse, AC, Firth, FCN, Moghadam, PZ, Fairen Jimenez, D, Gaultois, MW, Hill, JA, Magdysyuk, OV, Slater, B, Goodwin, AL, Grey, CP, Cliffe, Matt [0000-0002-0408-7647], Wu, Yue [0000-0003-2874-8267], Lee, Jeongjae [0000-0003-4294-4993], Forse, Alexander [0000-0001-9592-9821], Firth, Francesca [0000-0002-1209-2702], Fairen Jimenez, David [0000-0002-5013-1194], Gaultois, Michael [0000-0003-2172-2507], Grey, Clare [0000-0001-5572-192X], and Apollo - University of Cambridge Repository
- Subjects
0302 Inorganic Chemistry - Abstract
We report a hafnium-containing MOF, hcp UiO-67(Hf), which is a ligand-deficient layered analogue of the face-centered cubic fcu UiO-67(Hf). hcp UiO-67 accommodates its lower ligand:metal ratio compared to fcu UiO-67 through a new structural mechanism: the formation of a condensed "double cluster" (Hf$_{12}$O$_{8}$(OH)$_{14}$), analogous to the condensation of coordination polyhedra in oxide frameworks. In oxide frameworks, variable stoichiometry can lead to more complex defect structures, e.g., crystallographic shear planes or modules with differing compositions, which can be the source of further chemical reactivity; likewise, the layered hcp UiO-67 can react further to reversibly form a two-dimensional metal-organic framework, hxl UiO-67. Both three-dimensional hcp UiO-67 and two-dimensional hxl UiO-67 can be delaminated to form metal-organic nanosheets. Delamination of hcp UiO-67 occurs through the cleavage of strong hafnium-carboxylate bonds and is effected under mild conditions, suggesting that defect-ordered MOFs could be a productive route to porous two-dimensional materials.
- Published
- 2017
4. Mesoscale polarization by geometric frustration in columnar supramolecular crystals
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Zehe, CS, Hill, JA, Funnell, NP, Kreger, K, van der Zwan, KP, Goodwin, AL, Schmidt, H-W, and Senker, J
- Abstract
Columnar supramolecular phases with polarization along the columnar axis have potential for the development of ultrahigh-density memories as every single column might function as a memory element. By investigating structure and disorder for four columnar benzene-1,3,5-trisamides by total X-ray scattering and DFT calculations, we demonstrate that the column orientation, and thus the columnar dipole moment, is receptive to geometric frustration if the columns aggregate in a hexagonal rod packing. The frustration suppresses conventional antiferroelectric order and heightens the sensitivity towards collective intercolumnar packing effects. The latter finding allows for the building up of mesoscale domains with spontaneous polarization. Our results suggest how the complex interplay between steric and electrostatic interactions is influenced by a straightforward chemical design of the molecular synthons to create spontaneous polarization and to adjust mesoscale domain size.
- Published
- 2017
5. Organic crystals: Packing down
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Goodwin, AL
- Abstract
Barbour and co-workers have defined a crystal of (S,S)-octa-3,5-diyn-2,7- diol, the packing arrangement of an organic dumbbell-shaped molecule, which is expected to bring about a large thermal contraction of its crystal lattice. The dumbbells stack such that the hydrogen bonds at their ends form helices running parallel to one of the crystal axes. This arrangement connects the molecules in a similar way to the flexible networks suggesting the large thermal expansion between molecules might also bring about NT. Barbour's crystal is held together between the molecules and hydrogen bonds between the OH groups at either end of the dumbells. The results of Barbour and co-workers highlight the importance of looking to weakly bound materials for extreme, and extremely useful, mechanical behavior.
- Published
- 2016
6. Nanomaterials: The ins and outs of thermal expansion
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Goodwin, AL
- Abstract
Most materials expand when they are heated, but some contract instead. A record value of this effect - known as negative thermal expansion - has now been observed in magnetic nanocrystals. © 2008 Macmillan Publishers Limited. All rights reserved.
- Published
- 2016
7. Spin correlations in Ca3Co2O6: Polarized-neutron diffraction and Monte Carlo study
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Paddison, JAM, Agrestini, S, Lees, MR, Fleck, CL, Deen, PP, Goodwin, AL, Stewart, JR, and Petrenko, OA
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Condensed Matter::Strongly Correlated Electrons - Abstract
We present polarized-neutron diffraction measurements of the Ising-type spin-chain compound Ca3Co2O6 above and below the magnetic ordering temperature TN. Below TN, a clear evolution from a pure spin-density wave (SDW) structure to a mixture of SDW and commensurate antiferromagnet (CAFM) structures is observed on cooling. For a rapidly cooled sample, the majority phase at low temperature is the SDW, while if the cooling is performed sufficiently slowly, then the SDW and the CAFM structure coexist between 1.5 and 10 K. Above TN, we use Monte Carlo methods to analyze the magnetic diffuse scattering data. We show that both intrachain and interchain correlations persist above TN, but are essentially decoupled. Intrachain correlations resemble the one-dimensional ferromagnetic Ising model, while interchain correlations resemble the frustrated triangular-lattice antiferromagnet. Using previously published bulk property measurements and our neutron diffraction data, we obtain values of the ferromagnetic and antiferromagnetic exchange interactions and the single-ion anisotropy. © 2014 American Physical Society.
- Published
- 2016
8. Design of crystal-like aperiodic solids with selective disorder-phonon coupling
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Overy, AR, Cairns, AB, Cliffe, MJ, Simonov, A, Tucker, MG, and Goodwin, AL
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Science & Technology ,PEROVSKITE ,PHASE ,ICE ,ORDER ,FRAMEWORK ,STATE ,STATISTICS ,DIMERS ,cond-mat.mtrl-sci ,Multidisciplinary Sciences ,LATTICE ,MD Multidisciplinary ,Science & Technology - Other Topics ,SCATTERING - Published
- 2016
9. Advances in the treatment of patients with pancreatic cancer: improvement in symptoms and survival time.
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Von Hoff, DD, Goodwin, AL, and Garcia, L
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- 1998
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10. Lip service?
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Smith, John and Goodwin, Al
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PUBLIC finance , *GOVERNMENT aid , *GOVERNMENT programs - Abstract
The article focuses on the introduction of equity funding competitions (EFCs) in Private Finance Initiative (PFI) projects by Her Majesty's Treasury in Great Britain. The EFCs had created a confusion on PFI practitioners because government representatives have been vague in giving details of how the concept would work in practice and on the timetable for its implementation. The vagueness of information has become a challenge to practitioners because it create an obstacle for the project.
- Published
- 2007
11. Learning From Country: Aboriginal-Led Country-Centered Learning for Preservice Teachers
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Katrina Thorpe, Lee, WO, Brown, P, Goodwin, AL, and Green, A
- Published
- 2022
12. In Situ Observation of Topotactic Linker Reorganization in the Aperiodic Metal-Organic Framework TRUMOF-1.
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Greenbaum G, Doheny PW, Paraoan RAI, Kholina Y, Michalik S, Cassidy SJ, Yeung HH, and Goodwin AL
- 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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- 2024
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13. When can we trust structural models derived from pair distribution function measurements?
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Maffettone PM, Fletcher WJK, Nicholas TC, Deringer VL, Allison JR, Smith LJ, and Goodwin AL
- Abstract
The pair distribution function (PDF) is an important metric for characterising structure in complex materials, but it is well known that meaningfully different structural models can sometimes give rise to equivalent PDFs. In this paper, we discuss the use of model likelihoods as a general approach for discriminating between such homometric structure solutions. Drawing on two main case studies-one concerning the structure of a small peptide and the other amorphous calcium carbonate-we show how consideration of model likelihood can help drive robust structure solution, even in cases where the PDF is particularly information-poor. The obvious thread of these individual case studies is the potential role for machine-learning approaches to help guide structure determination from the PDF, and our paper finishes with some forward-looking discussion along these lines.
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- 2024
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14. Enhanced elastic stability of a topologically disordered crystalline metal-organic framework.
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Meekel EG, Partridge P, Paraoan RAI, Levinsky JJB, Slater B, Hobday CL, and Goodwin AL
- 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., (© 2024. The Author(s).)
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- 2024
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15. Parent attitudes towards data sharing in developmental science.
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Begum Ali J, Holman R, Goodwin AL, Heraty S, and Jones EJH
- Abstract
Background: Data sharing in developmental science is increasingly encouraged, supported by funder and publisher mandates for open data access. Data sharing can accelerate discovery, link researchers with high quality analytic expertise to researchers with large datasets and democratise the research landscape to enable researchers with limited funding to access large sample sizes. However, there are also significant privacy and security concerns, in addition to conceptual and ethical considerations. These are particularly acute for developmental science, where child participants cannot consent themselves. As we move forward into a new era of data openness, it is essential that we adequately represent the views of stakeholder communities in designing data sharing efforts., Methods: We conducted a comprehensive survey of the opinions of 195 parents on data sharing in developmental science. Survey themes included how widely parents are willing to share their child's data, which type of organisations they would share the data with and the type of consent they would be comfortable providing., Results: Results showed that parents were generally supportive of curated, but not open, data sharing. In addition to individual privacy and security concerns, more altruistic considerations around the purpose of research were important. Parents overwhelmingly supported nuanced consenting models in which preferences for particular types of data sharing could be changed over time. This model is different to that implemented in the vast majority of developmental science research and is contrary to many funder or publisher mandates., Conclusions: The field should look to create shared repositories that implement features such as dynamic consent and mechanisms for curated sharing that allow consideration of the scientific questions addressed. Better communication and outreach are required to build trust in data sharing, and advanced analytic methods will be required to understand the impact of selective sharing on reproducibility and representativeness of research datasets., Competing Interests: No competing interests were disclosed., (Copyright: © 2024 Begum Ali J et al.)
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- 2024
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16. Local Structure and Dynamics in MPt(CN) 6 Prussian Blue Analogues.
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Harbourne EA, Barker H, Guéroult Q, Cattermull J, Nagle-Cocco LAV, Roth N, Evans JSO, Keen DA, and Goodwin AL
- 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., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)- Published
- 2024
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17. Understanding Defects in Amorphous Silicon with Million-Atom Simulations and Machine Learning.
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Morrow JD, Ugwumadu C, Drabold DA, Elliott SR, Goodwin AL, and Deringer VL
- Abstract
The structure of amorphous silicon (a-Si) is widely thought of as a fourfold-connected random network, and yet it is defective atoms, with fewer or more than four bonds, that make it particularly interesting. Despite many attempts to explain such "dangling-bond" and "floating-bond" defects, respectively, a unified understanding is still missing. Here, we use advanced computational chemistry methods to reveal the complex structural and energetic landscape of defects in a-Si. We study an ultra-large-scale, quantum-accurate structural model containing a million atoms, and thousands of individual defects, allowing reliable defect-related statistics to be obtained. We combine structural descriptors and machine-learned atomic energies to develop a classification of the different types of defects in a-Si. The results suggest a revision of the established floating-bond model by showing that fivefold-bonded atoms in a-Si exhibit a wide range of local environments-analogous to fivefold centers in coordination chemistry. Furthermore, it is shown that fivefold (but not threefold) coordination defects tend to cluster together. Our study provides new insights into one of the most widely studied amorphous solids, and has general implications for understanding defects in disordered materials beyond silicon alone., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)
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- 2024
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18. Percolation-Induced Ferrimagnetism from Vacancy Order in [Gua]Mn 1- x Fe 2 x /3 (HCOO) 3 Hybrid Perovskites.
- Author
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Bulled JM, Willis A, Faure Beaulieu Z, Cassidy SJ, Bruckmoser J, Boström HLB, and Goodwin AL
- Abstract
We report the magnetic behavior of the hybrid perovskites [Gua]Mn
1- x Fe2 x /3 □x /3 (HCOO)3 (0 ≤ x ≤ 0.88), showing that vacancy ordering drives bulk ferrimagnetism for x > 0.6. The behavior is rationalized in terms of a simple microscopic model of percolation-induced ferrimagnetism. Monte Carlo simulations driven by this model reproduce the experimental dependence of magnetic susceptibility on x and show that, at intermediate compositions, domains of short-range vacancy order lead to the emergence of local magnetization. Our results open up a new avenue for the design of multiferroic hybrid perovskites.- Published
- 2024
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19. Geometrically frustrated interactions drive structural complexity in amorphous calcium carbonate.
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Nicholas TC, Stones AE, Patel A, Michel FM, Reeder RJ, Aarts DGAL, Deringer VL, and Goodwin AL
- Abstract
Amorphous calcium carbonate is an important precursor for biomineralization in marine organisms. Key outstanding problems include understanding the structure of amorphous calcium carbonate and rationalizing its metastability as an amorphous phase. Here we report high-quality atomistic models of amorphous calcium carbonate generated using state-of-the-art interatomic potentials to help guide fits to X-ray total scattering data. Exploiting a recently developed inversion approach, we extract from these models the effective Ca⋯Ca interaction potential governing the structure. This potential contains minima at two competing distances, corresponding to the two different ways that carbonate ions bridge Ca
2+ -ion pairs. We reveal an unexpected mapping to the Lennard-Jones-Gauss model normally studied in the context of computational soft matter. The empirical model parameters for amorphous calcium carbonate take values known to promote structural complexity. We thus show that both the complex structure and its resilience to crystallization are actually encoded in the geometrically frustrated effective interactions between Ca2+ ions., (© 2023. The Author(s).)- Published
- 2024
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20. Torsional flexibility in zinc-benzenedicarboxylate metal-organic frameworks.
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Meekel EG, Nicholas TC, Slater B, and Goodwin AL
- Abstract
We explore the role and nature of torsional flexibility of carboxylate-benzene links in the structural chemistry of metal-organic frameworks (MOFs) based on Zn and benzenedicarboxlyate (bdc) linkers. A particular motivation is to understand the extent to which such flexibility is important in stabilising the unusual topologically aperiodic phase known as TRUMOF-1. We compare the torsion angle distributions of TRUMOF-1 models with those for crystalline Zn/1,3-bdc MOFs, including a number of new materials whose structures we report here. We find that both periodic and aperiodic Zn/1,3-bdc MOFs sample a similar range of torsion angles, and hence the formation of TRUMOF-1 does not require any additional flexibility beyond that already evident in chemically-related crystalline phases. Comparison with Zn/1,4-bdc MOFs does show, however, that the lower symmetry of the 1,3-bdc linker allows access to a broader range of torsion angles, reflecting a greater flexibility of this linker., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)
- Published
- 2023
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21. On the Origin of the Non-Arrhenius Na-ion Conductivity in Na 3 OBr.
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Darminto B, Rees GJ, Cattermull J, Hashi K, Diaz-Lopez M, Kuwata N, Turrell SJ, Milan E, Chart Y, Di Mino C, Jeong Lee H, Goodwin AL, and Pasta M
- Abstract
The sodium-rich antiperovskites (NaRAPs) with composition Na
3 OB (B=Br, Cl, I, BH4 , etc.) are a family of materials that has recently attracted great interest for application as solid electrolytes in sodium metal batteries. Non-Arrhenius ionic conductivities have been reported for these materials, the origin of which is poorly understood. In this work, we combined temperature-resolved bulk and local characterisation methods to gain an insight into the origin of this unusual behaviour using Na3 OBr as a model system. We first excluded crystallographic disorder on the anion sites as the cause of the change in activation energy; then identified the presence of a poorly crystalline impurities, not detectable by XRD, and elucidated their effect on ionic conductivity. These findings improve understanding of the processing-structure-properties relationships pertaining to NaRAPs and highlight the need to determine these relationships in other materials systems, which will accelerate the development of high-performance solid electrolytes., Competing Interests: The authors declare no conflict of interest., (© 2023 The Authors. Angewandte Chemie published by Wiley-VCH GmbH.)- Published
- 2023
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22. K-Ion Slides in Prussian Blue Analogues.
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Cattermull J, Roth N, Cassidy SJ, Pasta M, and Goodwin AL
- Abstract
We study the phenomenology of cooperative off-centering of K
+ ions in potassiated Prussian blue analogues (PBAs). The principal distortion mechanism by which this off-centering occurs is termed a "K-ion slide", and its origin is shown to lie in the interaction between local electrostatic dipoles that couple through a combination of electrostatics and elastic strain. Using synchrotron powder X-ray diffraction measurements, we determine the crystal structures of a range of low-vacancy K2 M[Fe(CN)6 ] PBAs (M = Ni, Co, Fe, Mn, Cd) and establish an empirical link between composition, temperature, and slide-distortion magnitude. Our results reflect the common underlying physics responsible for K-ion slides and their evolution with temperature and composition. Monte Carlo simulations driven by a simple model of dipolar interactions and strain coupling reproduce the general features of the experimental phase behavior. We discuss the implications of our study for optimizing the performance of PBA K-ion battery cathode materials and also its relevance to distortions in other, conceptually related, hybrid perovskites.- Published
- 2023
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23. Predicting Distortion Magnitudes in Prussian Blue Analogues.
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Cattermull J, Pasta M, and Goodwin AL
- Abstract
Based on simple electrostatic and harmonic potential considerations, we derive a straightforward expression linking the composition of a Prussian blue analogue (PBA) to its propensity to undergo collective structural distortions. We demonstrate the existence of a threshold value, below which PBAs are undistorted and above which PBAs distort by a degree that is controlled by a geometric tolerance factor. Our analysis rationalizes the presence, absence, and magnitude of distortions in a wide range of PBAs and distinguishes their structural chemistry from that of other hybrid perovskites.
- Published
- 2023
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24. Quantitative three-dimensional local order analysis of nanomaterials through electron diffraction.
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Schmidt EM, Klar PB, Krysiak Y, Svora P, Goodwin AL, and Palatinus L
- Abstract
Structure-property relationships in ordered materials have long been a core principle in materials design. However, the introduction of disorder into materials provides structural flexibility and thus access to material properties that are not attainable in conventional, ordered materials. To understand disorder-property relationships, the disorder - i.e., the local ordering principles - must be quantified. Local order can be probed experimentally by diffuse scattering. The analysis is notoriously difficult, especially if only powder samples are available. Here, we combine the advantages of three-dimensional electron diffraction - a method that allows single crystal diffraction measurements on sub-micron sized crystals - and three-dimensional difference pair distribution function analysis (3D-ΔPDF) to address this problem. In this work, we compare the 3D-ΔPDF from electron diffraction data with those obtained from neutron and x-ray experiments of yttria-stabilized zirconia (Zr
0.82 Y0.18 O1.91 ) and demonstrate the reliability of the proposed approach., (© 2023. Springer Nature Limited.)- Published
- 2023
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25. Coarse-grained versus fully atomistic machine learning for zeolitic imidazolate frameworks.
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Faure Beaulieu Z, Nicholas TC, Gardner JLA, Goodwin AL, and Deringer VL
- Abstract
Zeolitic imidazolate frameworks are widely thought of as being analogous to inorganic AB
2 phases. We test the validity of this assumption by comparing simplified and fully atomistic machine-learning models for local environments in ZIFs. Our work addresses the central question to what extent chemical information can be "coarse-grained" in hybrid framework materials.- Published
- 2023
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26. Tuning electronic and phononic states with hidden order in disordered crystals.
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Roth N and Goodwin AL
- Abstract
Disorder in crystals is rarely random, and instead involves local correlations whose presence and nature are hidden from conventional crystallographic probes. This hidden order can sometimes be controlled, but its importance for physical properties of materials is not well understood. Using simple models for electronic and interatomic interactions, we show how crystals with identical average structures but different types of hidden order can have very different electronic and phononic band structures. Increasing the strength of local correlations within hidden-order states can open band gaps and tune mode (de)localisation-both mechanisms allowing for fundamental changes in physical properties without long-range symmetry breaking. Taken together, our results demonstrate how control over hidden order offers a new mechanism for tuning material properties, orthogonal to the conventional principles of (ordered) structure/property relationships., (© 2023. The Author(s).)
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- 2023
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27. Anion-polarisation-directed short-range-order in antiperovskite Li 2 FeSO.
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Coles SW, Falkowski V, Geddes HS, Pérez GE, Booth SG, Squires AG, O'Rourke C, McColl K, Goodwin AL, Cussen SA, Clarke SJ, Islam MS, and Morgan BJ
- Abstract
Short-range ordering in cation-disordered cathodes can have a significant effect on their electrochemical properties. Here, we characterise the cation short-range order in the antiperovskite cathode material Li
2 FeSO, using density functional theory, Monte Carlo simulations, and synchrotron X-ray pair-distribution-function data. We predict partial short-range cation-ordering, characterised by favourable OLi4 Fe2 oxygen coordination with a preference for polar cis -OLi4 Fe2 over non-polar trans -OLi4 Fe2 configurations. This preference for polar cation configurations produces long-range disorder, in agreement with experimental data. The predicted short-range-order preference contrasts with that for a simple point-charge model, which instead predicts preferential trans -OLi4 Fe2 oxygen coordination and corresponding long-range crystallographic order. The absence of long-range order in Li2 FeSO can therefore be attributed to the relative stability of cis -OLi4 Fe2 and other non-OLi4 Fe2 oxygen-coordination motifs. We show that this effect is associated with the polarisation of oxide and sulfide anions in polar coordination environments, which stabilises these polar short-range cation orderings. We propose that similar anion-polarisation-directed short-range-ordering may be present in other heterocationic materials that contain cations with different formal charges. Our analysis illustrates the limitations of using simple point-charge models to predict the structure of cation-disordered materials, where other factors, such as anion polarisation, may play a critical role in directing both short- and long-range structural correlations., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)- Published
- 2023
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28. Direct interpretation of the X-ray and neutron three-dimensional difference pair distribution functions (3D-ΔPDFs) of yttria-stabilized zirconia.
- Author
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Schmidt EM, Neder RB, Martin JD, Minelli A, Lemée MH, and Goodwin AL
- Abstract
Three-dimensional difference pair distribution functions (3D-ΔPDFs) from X-ray and neutron diffraction experiments are reported for yttria-stabilized zirconia (Zr
0.82 Y0.18 O1.91 ). A quantitative analysis of the signatures in the three-dimensional difference pair distribution functions is used to establish that oxygen ions neighbouring a vacancy shift by 0.525 (5) Å along ⟨1, 0, 0⟩ towards the vacancy while metal ions neighbouring a vacancy shift by 0.465 (2) Å along ⟨1, 1, 1⟩ away from the vacancy. The neutron 3D-ΔPDF shows a tendency for vacancies to cluster along ⟨½, ½, ½⟩, which results in sixfold coordinated metal ions., (open access.)- Published
- 2023
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29. Impulsivity dimensions and their associations with disinhibited and actual eating behaviour.
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Goodwin AL, Butler GKL, and Nikčević AV
- Subjects
- Humans, Female, Surveys and Questionnaires, Self Report, Feeding Behavior, Impulsive Behavior physiology
- Abstract
Background: Previous research has suggested that there is an association between impulsivity, assessed via self-report measures and behaviourally, and disinhibited eating patterns, but it remains unclear which specific dimension of impulsivity is the most salient in this relationship. Furthermore, it remains uncertain whether any such associations would extend to actual eating behaviours and food consumption., Aims: The present study aimed to examine whether impulsivity, assessed both behaviourally and via self-report, is associated with self-reported disinhibited and actual eating behaviour in a controlled eating task., Method: 70 women from a community sample (aged 21-35) completed the Disinhibition subscale of the Three Factor Eating Questionnaire (TFEQ), the Barratt Impulsiveness Scale (BIS-11), the Matching Familiar Figures Task (MFFT-20), and a behavioural food consumption task., Results: Bivariate correlational analyses revealed significant associations between self-report measure of impulsivity, the scores on the MFFT-20 (assessing reflection impulsivity), and self-report measure of disinhibited eating. All these measures were associated with overall food consumption in a taste task, with reflection impulsivity, that is poor ability to reflect on information before making a decision, having the strongest association with the amount of food consumed. Self-reported impulsivity was most strongly associated with disinhibited eating. Partial correlations controlling for BMI and age did not diminish any significant correlations within these relationships., Conclusions: Significant associations between both trait and behavioural (reflection) impulsivity, and self-reported disinhibited eating and actual eating behaviour were demonstrated. The implications of these findings on uncontrolled eating patterns in real life are discussed., Competing Interests: Declaration of competing interest We confirm that there are no financial/personal interests or beliefs that could affect the objectivity of our work. There are no competing interests to declare., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2023
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30. Truchet-tile structure of a topologically aperiodic metal-organic framework.
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Meekel EG, Schmidt EM, Cameron LJ, Dharma AD, Windsor HJ, Duyker SG, Minelli A, Pope T, Lepore GO, Slater B, Kepert CJ, and Goodwin AL
- Abstract
When tiles decorated to lower their symmetry are joined together, they can form aperiodic and labyrinthine patterns. Such Truchet tilings offer an efficient mechanism of visual data storage related to that used in barcodes and QR codes. We show that the crystalline metal-organic framework [OZn
4 ][1,3-benzenedicarboxylate]3 (TRUMOF-1) is an atomic-scale realization of a complex three-dimensional Truchet tiling. Its crystal structure consists of a periodically arranged assembly of identical zinc-containing clusters connected uniformly in a well-defined but disordered fashion to give a topologically aperiodic microporous network. We suggest that this unusual structure emerges as a consequence of geometric frustration in the chemical building units from which it is assembled.- Published
- 2023
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31. Polarization from sliding molecular rotors.
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Senn MS and Goodwin AL
- Published
- 2022
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32. Uncovering the Interplay of Competing Distortions in the Prussian Blue Analogue K 2 Cu[Fe(CN) 6 ].
- Author
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Cattermull J, Sada K, Hurlbutt K, Cassidy SJ, Pasta M, and Goodwin AL
- Abstract
We report the synthesis, crystal structure, thermal response, and electrochemical behavior of the Prussian blue analogue (PBA) K
2 Cu[Fe(CN)6 ]. From a structural perspective, this is the most complex PBA yet characterized: its triclinic crystal structure results from an interplay of cooperative Jahn-Teller order, octahedral tilts, and a collective "slide" distortion involving K-ion displacements. These different distortions give rise to two crystallographically distinct K-ion channels with different mobilities. Variable-temperature X-ray powder diffraction measurements show that K-ion slides are the lowest-energy distortion mechanism at play, as they are the only distortion to be switched off with increasing temperature. Electrochemically, the material operates as a K-ion cathode with a high operating voltage and an improved initial capacity relative to higher-vacancy PBA alternatives. On charging, K+ ions are selectively removed from a single K-ion channel type, and the slide distortions are again switched on and off accordingly. We discuss the functional importance of various aspects of structural complexity in this system, placing our discussion in the context of other related PBAs., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)- Published
- 2022
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33. Interplay of thermal diffuse scattering and correlated compositional disorder in KCl 1-x Br x .
- Author
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Schmidt EM, Thomas S, Bulled JM, Minelli A, and Goodwin AL
- Subjects
- Monte Carlo Method, Thermal Conductivity, X-Rays, Phonons
- Abstract
Single-crystal X-ray diffuse scattering measurements are reported of the compositional series KCl
1-x Brx , a model system for the broader family of disordered rocksalts. Using a combination of Monte Carlo simulations and lattice dynamical calculations, we show that the observed diffuse scattering is well described in terms of (i) non-statistical anion distributions, (ii) local lattice relaxations accompanying Cl/Br substitution, and (iii) the contribution from low-energy phonons. It is found that a tendency for compositional domain formation broadens the thermal diffuse scattering by splitting and softening the acoustic phonon branches. This effect, which is strongest for intermediate compositions, is seen in both experiment and calculation alike. These results establish a link between local compositional order and unconventional lattice dynamics in this system, and reinforce emerging design principles of exploiting compositional fluctuations to tailor physical properties, such as thermal conductivity, that depend on phonon broadening., (open access.)- Published
- 2022
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34. Geometric Frustration on the Trillium Lattice in a Magnetic Metal-Organic Framework.
- Author
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Bulled JM, Paddison JAM, Wildes A, Lhotel E, Cassidy SJ, Pato-Doldán B, Gómez-Aguirre LC, Saines PJ, and Goodwin AL
- Abstract
In the dense metal-organic framework Na[Mn(HCOO)_{3}], Mn^{2+} ions (S=5/2) occupy the nodes of a "trillium" net. We show that the system is strongly magnetically frustrated: the Néel transition is suppressed well below the characteristic magnetic interaction strength; short-range magnetic order persists far above the Néel temperature; and the magnetic susceptibility exhibits a pseudo-plateau at 1/3-saturation magnetization. A simple model of nearest-neighbor Heisenberg antiferromagnetic and dipolar interactions accounts quantitatively for all observations, including an unusual 2-k magnetic ground state. We show that the relative strength of dipolar interactions is crucial to selecting this particular ground state. Geometric frustration within the classical spin liquid regime gives rise to a large magnetocaloric response at low applied fields that is degraded in powder samples as a consequence of the anisotropy of dipolar interactions.
- Published
- 2022
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- View/download PDF
35. Structural complexity in Prussian blue analogues.
- Author
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Cattermull J, Pasta M, and Goodwin AL
- Subjects
- Ferrocyanides
- Abstract
We survey the most important kinds of structural complexity in Prussian blue analogues, their implications for materials function, and how they might be controlled through judicious choice of composition. We focus on six particular aspects: octahedral tilts, A-site 'slides', Jahn-Teller distortions, A-site species and occupancy, hexacyanometallate vacancies, and framework hydration. The promising K-ion cathode material K
x Mn[Fe(CN)6 ]y serves as a recurrent example that illustrates many of these different types of complexity. Our article concludes with a discussion of how the interplay of various distortion mechanisms might be exploited to optimise the performance of this and other related systems, so as to aid in the design of next-generation PBA materials.- Published
- 2021
- Full Text
- View/download PDF
36. Recovering local structure information from high-pressure total scattering experiments.
- Author
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Herlihy A, Geddes HS, Sosso GC, Bull CL, Ridley CJ, Goodwin AL, Senn MS, and Funnell NP
- Abstract
High pressure is a powerful thermodynamic tool for exploring the structure and the phase behaviour of the crystalline state, and is now widely used in conventional crystallographic measurements. High-pressure local structure measurements using neutron diffraction have, thus far, been limited by the presence of a strongly scattering, perdeuterated, pressure-transmitting medium (PTM), the signal from which contaminates the resulting pair distribution functions (PDFs). Here, a method is reported for subtracting the pairwise correlations of the commonly used 4:1 methanol:ethanol PTM from neutron PDFs obtained under hydro-static compression. The method applies a molecular-dynamics-informed empirical correction and a non-negative matrix factorization algorithm to recover the PDF of the pure sample. Proof of principle is demonstrated, producing corrected high-pressure PDFs of simple crystalline materials, Ni and MgO, and benchmarking these against simulated data from the average structure. Finally, the first local structure determination of α-quartz under hydro-static pressure is presented, extracting compression behaviour of the real-space structure., (© Anna Herlihy et al. 2021.)
- Published
- 2021
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- View/download PDF
37. Visualization and Quantification of Geometric Diversity in Metal-Organic Frameworks.
- Author
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Nicholas TC, Alexandrov EV, Blatov VA, Shevchenko AP, Proserpio DM, Goodwin AL, and Deringer VL
- Abstract
With ever-growing numbers of metal-organic framework (MOF) materials being reported, new computational approaches are required for a quantitative understanding of structure-property correlations in MOFs. Here, we show how structural coarse-graining and embedding ("unsupervised learning") schemes can together give new insights into the geometric diversity of MOF structures. Based on a curated data set of 1262 reported experimental structures, we automatically generate coarse-grained and rescaled representations which we couple to a kernel-based similarity metric and to widely used embedding schemes. This approach allows us to visualize the breadth of geometric diversity within individual topologies and to quantify the distributions of local and global similarities across the structural space of MOFs. The methodology is implemented in an openly available Python package and is expected to be useful in future high-throughput studies., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)
- Published
- 2021
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38. Efficient fitting of single-crystal diffuse scattering in interaction space: a mean-field approach.
- Author
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Schmidt EM, Bulled JM, and Goodwin AL
- Abstract
The diffraction patterns of crystalline materials with strongly correlated disorder are characterized by the presence of structured diffuse scattering. Conventional analysis approaches generally seek to interpret this scattering either atomistically or in terms of pairwise (Warren-Cowley) correlation parameters. Here it is demonstrated how a mean-field methodology allows efficient fitting of diffuse scattering directly in terms of a microscopic interaction model. In this way the approach gives as its output the underlying physics responsible for correlated disorder. Moreover, the use of a very small number of parameters during fitting renders the approach surprisingly robust to data incompleteness, a particular advantage when seeking to interpret single-crystal diffuse scattering measured in complex sample environments. As the basis of this proof-of-concept study, a toy model is used based on strongly correlated disorder in diammine mercury(II) halides., (© Ella M. Schmidt et al. 2022.)
- Published
- 2021
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39. Extracting interface correlations from the pair distribution function of composite materials.
- Author
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Geddes HS, Hutchinson HD, Ha AR, Funnell NP, and Goodwin AL
- Abstract
Using a non-negative matrix factorisation (NMF) approach, we show how the pair distribution function (PDF) of complex mixtures can be deconvolved into the contributions from the individual phase components and also the interface between phases. Our focus is on the model system Fe∥Fe
3 O4 . We establish proof-of-concept using idealised PDF data generated from established theory-driven models of the Fe∥Fe3 O4 interface. Using X-ray total scattering measurements for corroded Fe samples, and employing our newly-developed NMF analysis, we extract the experimental interface PDF ('iPDF') for this same system. We find excellent agreement between theory and experiment. The implications of our results in the broader context of interface characterisation for complex functional materials are discussed.- Published
- 2021
- Full Text
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40. Adaptive response of a metal-organic framework through reversible disorder-disorder transitions.
- Author
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Ehrling S, Reynolds EM, Bon V, Senkovska I, Gorelik TE, Evans JD, Rauche M, Mendt M, Weiss MS, Pöppl A, Brunner E, Kaiser U, Goodwin AL, and Kaskel S
- Abstract
The ultrahigh porosity and varied functionalities of porous metal-organic frameworks make them excellent candidates for applications that range widely from gas storage and separation to catalysis and sensing. An interesting feature of some frameworks is the ability to open their pores to a specific guest, enabling highly selective separation. A prerequisite for this is bistability of the host structure, which enables the framework to breathe, that is, to switch between two stability minima in response to its environment. Here we describe a porous framework DUT-8(Ni)-which consists of nickel paddle wheel clusters and carboxylate linkers-that adopts a configurationally degenerate family of disordered states in the presence of specific guests. This disorder originates from the nonlinear linkers arranging the clusters in closed loops of different local symmetries that in turn propagate as complex tilings. Solvent exchange stimulates the formation of distinct disordered frameworks, as demonstrated by high-resolution transmission electron microscopy and diffraction techniques. Guest exchange was shown to stimulate repeatable switching transitions between distinct disorder states.
- Published
- 2021
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41. Revisiting metal fluorides as lithium-ion battery cathodes.
- Author
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Hua X, Eggeman AS, Castillo-Martínez E, Robert R, Geddes HS, Lu Z, Pickard CJ, Meng W, Wiaderek KM, Pereira N, Amatucci GG, Midgley PA, Chapman KW, Steiner U, Goodwin AL, and Grey CP
- Abstract
Metal fluorides, promising lithium-ion battery cathode materials, have been classified as conversion materials due to the reconstructive phase transitions widely presumed to occur upon lithiation. We challenge this view by studying FeF
3 using X-ray total scattering and electron diffraction techniques that measure structure over multiple length scales coupled with density functional theory calculations, and by revisiting prior experimental studies of FeF2 and CuF2 . Metal fluoride lithiation is instead dominated by diffusion-controlled displacement mechanisms, and a clear topological relationship between the metal fluoride F- sublattices and that of LiF is established. Initial lithiation of FeF3 forms FeF2 on the particle's surface, along with a cation-ordered and stacking-disordered phase, A-Lix Fey F3 , which is structurally related to α-/β-LiMn2+ Fe3+ F6 and which topotactically transforms to B- and then C-Lix Fey F3 , before forming LiF and Fe. Lithiation of FeF2 and CuF2 results in a buffer phase between FeF2 /CuF2 and LiF. The resulting principles will aid future developments of a wider range of isomorphic metal fluorides.- Published
- 2021
- Full Text
- View/download PDF
42. Negative X-ray expansion in cadmium cyanide.
- Author
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Coates CS, Murray CA, Boström HLB, Reynolds EM, and Goodwin AL
- Abstract
Cadmium cyanide, Cd(CN)
2 , is a flexible coordination polymer best studied for its strong and isotropic negative thermal expansion (NTE) effect. Here we show that this NTE is actually X-ray-exposure dependent: Cd(CN)2 contracts not only on heating but also on irradiation by X-rays. This behaviour contrasts that observed in other beam-sensitive materials, for which X-ray exposure drives lattice expansion. We call this effect 'negative X-ray expansion' (NXE) and suggest its origin involves an interaction between X-rays and cyanide 'flips'; in particular, we rule out local heating as a possible mechanism. Irradiation also affects the nature of a low-temperature phase transition. Our analysis resolves discrepancies in NTE coefficients reported previously on the basis of X-ray diffraction measurements, and we establish the 'true' NTE behaviour of Cd(CN)2 across the temperature range 150-750 K. The interplay between irradiation and mechanical response in Cd(CN)2 highlights the potential for exploiting X-ray exposure in the design of functional materials.- Published
- 2021
- Full Text
- View/download PDF
43. Spin-ice physics in cadmium cyanide.
- Author
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Coates CS, Baise M, Schmutzler A, Simonov A, Makepeace JW, Seel AG, Smith RI, Playford HY, Keen DA, Siegel R, Senker J, Slater B, and Goodwin AL
- Abstract
Spin-ices are frustrated magnets that support a particularly rich variety of emergent physics. Typically, it is the interplay of magnetic dipole interactions, spin anisotropy, and geometric frustration on the pyrochlore lattice that drives spin-ice formation. The relevant physics occurs at temperatures commensurate with the magnetic interaction strength, which for most systems is 1-5 K. Here, we show that non-magnetic cadmium cyanide, Cd(CN)
2 , exhibits analogous behaviour to magnetic spin-ices, but does so on a temperature scale that is nearly two orders of magnitude greater. The electric dipole moments of cyanide ions in Cd(CN)2 assume the role of magnetic pseudospins, with the difference in energy scale reflecting the increased strength of electric vs magnetic dipolar interactions. As a result, spin-ice physics influences the structural behaviour of Cd(CN)2 even at room temperature.- Published
- 2021
- Full Text
- View/download PDF
44. Hybrid Perovskites, Metal-Organic Frameworks, and Beyond: Unconventional Degrees of Freedom in Molecular Frameworks.
- Author
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Boström HLB and Goodwin AL
- Abstract
ConspectusThe structural degrees of freedom of a solid material are the various distortions most straightforwardly activated by external stimuli such as temperature, pressure, or adsorption. One of the most successful design strategies in materials chemistry involves controlling these individual distortions to produce useful collective functional responses. In a ferroelectric such as lead titanate, for example, the key degree of freedom involves asymmetric displacements of Pb
2+ and Ti4+ cations; it is by coupling these together that the system as a whole interacts with external electric fields. Collective rotations of the polyhedral units in oxide ceramics are another commonly exploited distortion, driving anomalous behavior such as negative thermal expansion-the counterintuitive phenomenon of volume contraction on heating. An exciting development in the field has been to take advantage of the interplay between different distortion types: generating polarization by combining two different polyhedral rotations, for example. In this way, degrees of freedom act as geometric "elements" that can themselves be combined to engineer materials with new and interesting properties. Just as the discovery of new chemical elements quite obviously diversified chemical space, we might expect that identifying new and different types of structural degrees of freedom to be an important strategy for developing new kinds of functional materials. In this context, the broad family of molecular frameworks is emerging as an extraordinarily fertile source of new and unanticipated distortion types, the vast majority of which have no parallel in the established families of conventional solid-state chemistry.Framework materials are solids whose structures are assembled from two fundamental components: nodes and linkers. Quite simply, linkers join the nodes together to form scaffolding-like networks that extend from the atomic to the macroscopic scale. These structures usually contain cavities, which can also accommodate additional ions for charge balance. In the well-established systems-such as lead titanate-node, linker, and extra-framework ions are all individual atoms (Ti, O, and Pb, respectively). But in molecular frameworks, at least one of these components is a molecule.In this Account, we survey the unconventional degrees of freedom introduced through the simple act of replacing atoms by molecules. Our motivation is to understand the role these new distortions play (or might be expected to play) in different materials properties. The various degrees of freedom themselves-unconventional rotational, translational, orientational, and conformational states-are summarized and described in the context of relevant experimental examples. The much-improved prospect for generating emergent functionalities by combining these new distortion types is then discussed. We highlight a number of directions for future research-including the design and application of hierarchically structured phases of matter intermediate to solids and liquid crystals-which serve to highlight the extraordinary possibilities for this nascent field.- Published
- 2021
- Full Text
- View/download PDF
45. Mechanisms for collective inversion-symmetry breaking in dabconium perovskite ferroelectrics.
- Author
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Allen DJW, Bristowe NC, Goodwin AL, and Yeung HH
- Abstract
Dabconium hybrid perovskites include a number of recently-discovered ferroelectric phases with large spontaneous polarisations. The origin of ferroelectric response has been rationalised in general terms in the context of hydrogen bonding, covalency, and strain coupling. Here we use a combination of simple theory, Monte Carlo simulations, and density functional theory calculations to assess the ability of these microscopic ingredients-together with the always-present through-space dipolar coupling-to account for the emergence of polarisation in these particular systems whilst not in other hybrid perovskites. Our key result is that the combination of A-site polarity, preferred orientation along 〈111〉 directions, and ferroelastic strain coupling drives precisely the ferroelectric transition observed experimentally. We rationalise the absence of polarisation in many hybrid perovskites, and arrive at a set of design rules for generating FE examples beyond the dabconium family alone., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)
- Published
- 2021
- Full Text
- View/download PDF
46. Single-step synthesis and interface tuning of core-shell metal-organic framework nanoparticles.
- Author
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Orr KWP, Collins SM, Reynolds EM, Nightingale F, Boström HLB, Cassidy SJ, Dawson DM, Ashbrook SE, Magdysyuk OV, Midgley PA, Goodwin AL, and Yeung HH
- Abstract
Control over the spatial distribution of components in metal-organic frameworks has potential to unlock improved performance and new behaviour in separations, sensing and catalysis. We report an unprecedented single-step synthesis of multi-component metal-organic framework (MOF) nanoparticles based on the canonical ZIF-8 (Zn) system and its Cd analogue, which form with a core-shell structure whose internal interface can be systematically tuned. We use scanning transmission electron microscopy, X-ray energy dispersive spectroscopy and a new composition gradient model to fit high-resolution X-ray diffraction data to show how core-shell composition and interface characteristics are intricately controlled by synthesis temperature and reaction composition. Particle formation is investigated by in situ X-ray diffraction, which reveals that the spatial distribution of components evolves with time and is determined by the interplay of phase stability, crystallisation kinetics and diffusion. This work opens up new possibilities for the control and characterisation of functionality, component distribution and interfaces in MOF-based materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)
- Published
- 2021
- Full Text
- View/download PDF
47. Function from configurational degeneracy in disordered framework materials.
- Author
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Reynolds EM, Wolpert EH, Overy AR, Mizzi L, Simonov A, Grima JN, Kaskel S, and Goodwin AL
- Abstract
The existence of correlated disorder in molecular frameworks is an obvious mechanism by which unusual cooperative phenomena might be realised. We show that the use of local-symmetry lowering approaches can allow ostensibly high-symmetry framework structures to harbour exotic disordered states often studied in the context of spin lattice models. These states exhibit strongly cooperative behaviour that might be exploited in anomalous mechanical, host/guest, and information storage behaviour. Our contribution focuses in particular on the concepts of (i) combinatorial mechanics, (ii) adaptive flexibility, and (iii) error-correcting data storage in framework materials.
- Published
- 2021
- Full Text
- View/download PDF
48. Novel computational tools: general discussion.
- Author
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Bennett TD, Brammer L, Coudert FX, Evans JD, Fischer M, Goodwin AL, Jiang J, Kaskel S, Kitagawa S, Krause S, Lee JM, Matsuda R, Rogge SMJ, Ryder MR, Schmid R, Tarzia A, van der Veen MA, and Van Speybroeck V
- Published
- 2021
- Full Text
- View/download PDF
49. Non-equilibrium metal oxides via reconversion chemistry in lithium-ion batteries.
- Author
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Hua X, Allan PK, Gong C, Chater PA, Schmidt EM, Geddes HS, Robertson AW, Bruce PG, and Goodwin AL
- Abstract
Binary metal oxides are attractive anode materials for lithium-ion batteries. Despite sustained effort into nanomaterials synthesis and understanding the initial discharge mechanism, the fundamental chemistry underpinning the charge and subsequent cycles-thus the reversible capacity-remains poorly understood. Here, we use in operando X-ray pair distribution function analysis combining with our recently developed analytical approach employing Metropolis Monte Carlo simulations and non-negative matrix factorisation to study the charge reaction thermodynamics of a series of Fe- and Mn-oxides. As opposed to the commonly believed conversion chemistry forming rocksalt FeO and MnO, we reveal the two oxide series topotactically transform into non-native body-centred cubic FeO and zincblende MnO via displacement-like reactions whose kinetics are governed by the mobility differences between displaced species. These renewed mechanistic insights suggest avenues for the future design of metal oxide materials as well as new material synthesis routes using electrochemically-assisted methods.
- Published
- 2021
- Full Text
- View/download PDF
50. Ring structure of selected two-dimensional procrystalline lattices.
- Author
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Ormrod Morley D, Goodwin AL, and Wilson M
- Abstract
Recent work has introduced the term "procrystalline" to define systems which lack translational symmetry but have an underlying high-symmetry lattice. The properties of five such two-dimensional (2D) lattices are considered in terms of the topologies of rings which may be formed from three-coordinate sites only. Parent lattices with full coordination numbers of four, five, and six are considered, with configurations generated using a Monte Carlo algorithm. The different lattices are shown to generate configurations with varied ring distributions. The different constraints imposed by the underlying lattices are discussed. Ring size distributions are obtained analytically for two of the simpler lattices considered (the square and trihexagonal nets). In all cases, the ring size distributions are compared to those obtained via a maximum entropy method. The configurations are analyzed with respect to the near-universal Lemaître curve (which connects the fraction of six-membered rings with the width of the ring size distribution) and three lattices are highlighted as rare examples of systems which generate configurations which do not map onto this curve. The assortativities are considered, which contain information on the degree of ordering of different sized rings within a given distribution. All of the systems studied show systematically greater assortativities when compared to those generated using a standard bond-switching method. Comparison is also made to two series of crystalline motifs which shown distinctive behavior in terms of both the ring size distributions and the assortativities. Procrystalline lattices are therefore shown to have fundamentally different behavior to traditional disordered and crystalline systems, indicative of the partial ordering of the underlying lattices.
- Published
- 2020
- Full Text
- View/download PDF
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