I11-High Resolution Powder Diffraction
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Alexandra
Morscher
,
Matthew S.
Dyer
,
Benjamin B.
Duff
,
Guopeng
Han
,
Jacinthe
Gamon
,
Luke
Daniels
,
Yun
Dang
,
T. Wesley
Surta
,
Craig M.
Robertson
,
Frédéric
Blanc
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[23666]
Open Access
Abstract: A hexagonal analogue, Li6SiO4Cl2, of the cubic lithium argyrodite family of solid electrolytes is isolated by a computation–experiment approach. We show that the argyrodite structure is equivalent to the cubic antiperovskite solid electrolyte structure through anion site and vacancy ordering within a cubic stacking of two close-packed layers. Construction of models that assemble these layers with the combination of hexagonal and cubic stacking motifs, both well known in the large family of perovskite structural variants, followed by energy minimization identifies Li6SiO4Cl2 as a stable candidate composition. Synthesis and structure determination demonstrate that the material adopts the predicted lithium site-ordered structure with a low lithium conductivity of ∼10–10 S cm–1 at room temperature and the predicted hexagonal argyrodite structure above an order–disorder transition at 469.3(1) K. This transition establishes dynamic Li site disorder analogous to that of cubic argyrodite solid electrolytes in hexagonal argyrodite Li6SiO4Cl2 and increases Li-ion mobility observed via NMR and AC impedance spectroscopy. The compositional flexibility of both argyrodite and perovskite alongside this newly established structural connection, which enables the use of hexagonal and cubic stacking motifs, identifies a wealth of unexplored chemistry significant to the field of solid electrolytes.
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Mar 2021
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I11-High Resolution Powder Diffraction
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Craig I.
Hiley
,
Kenneth K.
Inglis
,
Marco
Zanella
,
Jiliang
Zhang
,
Troy D.
Manning
,
Matthew S.
Dyer
,
Tilen
Knaflič
,
Denis
Arčon
,
Frédéric
Blanc
,
Kosmas
Prassides
,
Matthew J.
Rosseinsky
Open Access
Abstract: The products of the solid-state reactions between potassium metal and tetracene (K:Tetracene, 1:1, 1.5:1, and 2:1) are fully structurally characterized. Synchrotron X-ray powder diffraction shows that only K2Tetracene forms under the reaction conditions studied, with unreacted tetracene always present for x < 2. Diffraction and 13C MAS NMR show that K2Tetracene has a crystal structure that is analogous to that of K2Pentacene, but with the cations ordered on two sites because of the influence of the length of the hydrocarbon on possible cation positions. K2Tetracene is a nonmagnetic insulator, thus further questioning the nature of reported superconductivity in this class of materials.
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Aug 2020
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I19-Small Molecule Single Crystal Diffraction
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Catherine M.
Aitchison
,
Michael
Sachs
,
Marc A.
Little
,
Liam
Wilbraham
,
Nick J.
Brownbill
,
Christopher M.
Kane
,
Frédéric
Blanc
,
Martijn
Zwijnenburg
,
James R.
Durrant
,
Reiner S.
Sprick
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[21726]
Open Access
Abstract: So far, most organic semiconductor photocatalysts for solar fuels production have been linear polymers or polymeric networks with a broad distribution of molecular weights. Here, we study a series of molecular dibenzo[b,d]thiophene sulfone and fluorene oligomers as well-defined model systems to probe the relationship between photocatalytic activity and structural features such as chain length and planarity. The hydrogen evolution rate was found to vary significantly with bridge head atom, chain length, and backbone twisting. A trimer (S3) of only three repeat units has excellent activity for proton reduction with an EQE of 8.8% at 420 nm, approaching the activity of its polymer analogue and demonstrating that high molar masses are not a prerequisite for good activity. The dynamics of long-lived electrons generated under illumination in the S3 oligomer are also very similar to the corresponding polymer, both under transient and constant irradiation conditions.
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Jul 2020
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I11-High Resolution Powder Diffraction
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Jacinthe
Gamon
,
Benjamin B.
Duff
,
Matthew S.
Dyer
,
Christopher
Collins
,
Luke M.
Daniels
,
T. Wesley
Surta
,
Paul M.
Sharp
,
Michael W.
Gaultois
,
Frédéric
Blanc
,
John B.
Claridge
,
Matthew
Rosseinsky
Abstract: With the goal of finding new lithium solid electrolytes by a combined computational-experimental method, the exploration of the Li-Al-O-S phase field resulted in the discovery of a new sulphide Li3AlS3. The structure of the new phase was determined through an approach combining synchrotron X-ray and neutron diffraction with 6Li and 27Al magic angle spinning nuclear magnetic resonance spectroscopy, and revealed a highly ordered cationic polyhedral network within a sulphide anion hcp-type sublattice. The originality of the structure relies on the presence of Al2S6 repeating dimer units consisting of two edge-shared Al tetrahedra. We find that, in this structure type consisting of alternating tetrahedral layers with Li-only polyhedra layers, the formation of these dimers is constrained by the Al/S ratio of 1/3. Moreover, by comparing this structure to similar phases such as Li5AlS4 and Li4.4Al0.2Ge0.3S4 ((Al+Ge)/S = 1/4), we discovered that the Al2S6 dimers not only influence atomic displacements and Li polyhedral distortions, but also determine the overall Li polyhedral arrangement within the hcp lattice, leading to the presence of highly ordered vacancies in both the tetrahedral and Li-only layer. AC-impedance measurements revealed a low lithium mobility, which is strongly impacted by the presence of ordered vacancies. Finally, a composition-structure-property relationship understanding was developed to explain the extent of lithium mobility in this structure type.
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Oct 2019
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I11-High Resolution Powder Diffraction
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Bernhard T.
Leube
,
Kenneth K.
Inglis
,
Elliot
Carrington
,
Paul M.
Sharp
,
J. Felix
Shin
,
Alex R.
Neale
,
Troy D.
Manning
,
Michael J.
Pitcher
,
Laurence
Hardwick
,
Matthew S.
Dyer
,
Frédéric
Blanc
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Abstract: In order to understand the structural and compositional factors controlling lithium transport in sulfides, we explored the Li5AlS4 – Li4GeS4 phase field for new materials. Both parent compounds are defined structurally by a hexagonal close packed sulfide lattice, where distinct arrangements of tetrahedral metal sites give Li5AlS4 a layered structure and Li4GeS4 a three dimensional structure related to γ-Li3PO4. The combination of the two distinct structural motifs is expected to lead to new structural chemistry. We identified the new crystalline phase Li4.4Al0.4Ge0.6S4, and investigated the structure and Li+ ion dynamics of the family of structurally related materials Li4.4M0.4M’0.6S4 (M = Al3+, Ga3+ and M’= Ge4+, Sn4+). We used neutron diffraction to solve the full structures of the Al-homologues, which adopt a layered close-packed structure with a new arrangement of tetrahedral (M/M’) sites and a novel combination of ordered and disordered lithium vacancies. AC impedance spectroscopy revealed lithium conductivities in the range 3(2) x 10-6 to 4.3(3) x 10-5 S cm-1 at room temperature with activation energies between 0.43(1) and 0.38(1) eV. Electrochemical performance was tested in a plating and stripping experiment against Li metal electrodes and showed good stability of the Li4.4Al0.4Ge0.6S4 phase over 200 hours. A combination of variable temperature 7Li solid state nuclear magnetic resonance spectroscopy and ab initio molecular dynamics calculations on selected phases showed that two dimensional diffusion with a low energy barrier of 0.17 eV is responsible for long-range lithium transport, with diffusion pathways mediated by the disordered vacancies while the ordered vacancies do not contribute to the conductivity. This new structural family of sulfide Li+ ion conductors offers insight into the role of disordered vacancies on Li+ ion conductivity mechanisms in hexagonally close packed sulfides that can inform future materials design.
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Sep 2018
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I15-1-X-ray Pair Distribution Function (XPDF)
I22-Small angle scattering & Diffraction
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Louis
Longley
,
Sean
Collins
,
Chao
Zhou
,
Glen J.
Smales
,
Sarah E.
Norman
,
Nick J.
Brownbill
,
Christopher W.
Ashling
,
Philip A.
Chater
,
Robert
Tovey
,
Carola-bibiane
Schönlieb
,
Thomas F.
Headen
,
Nicholas J.
Terrill
,
Yuanzheng
Yue
,
Andrew J.
Smith
,
Frédéric
Blanc
,
David
Keen
,
Paul A.
Midgley
,
Thomas
Bennett
Diamond Proposal Number(s):
[171151, 18236]
Open Access
Abstract: The liquid and glass states of metal–organic frameworks (MOFs) have recently become of interest due to the potential for liquid-phase separations and ion transport, alongside the fundamental nature of the latter as a new, fourth category of melt-quenched glass. Here we show that the MOF liquid state can be blended with another MOF component, resulting in a domain structured MOF glass with a single, tailorable glass transition. Intra-domain connectivity and short range order is confirmed by nuclear magnetic resonance spectroscopy and pair distribution function measurements. The interfacial binding between MOF domains in the glass state is evidenced by electron tomography, and the relationship between domain size and Tg investigated. Nanoindentation experiments are also performed to place this new class of MOF materials into context with organic blends and inorganic alloys.
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Jun 2018
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I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
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Kecheng
Jie
,
Ming
Liu
,
Yujuan
Zhou
,
Marc A.
Little
,
Angeles
Pulido
,
Samantha Y.
Chong
,
Andrew
Stephenson
,
Ashlea R.
Hughes
,
Fumiyasu
Sakakibara
,
Tomoki
Ogoshi
,
Frédéric
Blanc
,
Graeme M.
Day
,
Feihe
Huang
,
Andrew I.
Cooper
Diamond Proposal Number(s):
[15777, 12336, 17193]
Abstract: The energy-efficient separation of alkylaromatic compounds is a major industrial sustainability challenge. The use of selectively porous extended frameworks, such as zeolites or metal–organic frameworks, is one solution to this problem. Here, we studied a flexible molecular material, perethylated pillar[n]arene crystals (n = 5, 6), which can be used to separate C8 alkylaromatic compounds. Pillar[6]arene is shown to separate para-xylene from its structural isomers, meta-xylene and ortho-xylene, with 90% specificity in the solid state. Selectivity is an intrinsic property of the pillar[6]arene host, with the flexible pillar[6]arene cavities adapting during adsorption thus enabling preferential adsorption of para-xylene in the solid state. The flexibility of pillar[6]arene as a solid sorbent is rationalized using molecular conformer searches and crystal structure prediction (CSP) combined with comprehensive characterization by X-ray diffraction and 13C solid state NMR spectroscopy. The CSP study, which takes into account the structural variability of pillar[6]arene, breaks new ground in its own right and showcases the feasibility of applying CSP methods to understand and ultimately to predict the behaviour of soft, adaptive molecular crystals.
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May 2018
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I11-High Resolution Powder Diffraction
I15-Extreme Conditions
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Diamond Proposal Number(s):
[12336, 9282]
Open Access
Abstract: Covalent organic frameworks (COFs) are network polymers with long-range positional order whose properties can be tuned using the isoreticular chemistry approach. Making COFs from strong bonds is challenging because irreversible rapid formation of the network produces amorphous materials with locked-in disorder. Reversibility in bond formation is essential to generate ordered networks, as it allows the error-checking that permits the network to crystallise, and so candidate network-forming chemistries such as amide that are irreversible under conventional low temperature bond-forming conditions have been underexplored. Here we show that we can prepare two- and three-dimensional covalent amide frameworks (CAFs) by devitrification of amorphous polyamide network polymers using high-temperature and high-pressure reaction conditions. In this way we have accessed reversible amide bond formation that allows crystalline order to develop. This strategy permits the direct synthesis of practically irreversible ordered amide networks that are stable thermally and under both strong acidic and basic hydrolytic conditions.
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Oct 2017
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I11-High Resolution Powder Diffraction
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Alma B.
Santibáñez-mendieta
,
Christophe
Didier
,
Kenneth K.
Inglis
,
Alex J.
Corkett
,
Michael
Pitcher
,
Marco
Zanella
,
J. Felix
Shin
,
Luke
Daniels
,
Aydar
Rakhmatullin
,
Ming
Li
,
Matthew S.
Dyer
,
John B.
Claridge
,
Frédéric
Blanc
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[12336]
Abstract: The structure and Li+ ion dynamics of a new class of ABO3 perovskite with Li on both the A- and B-sites are described. La3Li3W2O12 is synthesised by solid state reaction at 900°C and shown by powder X-ray diffraction to adopt the structure of a monoclinic double perovskite (A2)BBꞌO6, (La1.5Li0.5)WLiO6, with rock salt order of W6+ and Li+ on the B-site. High resolution powder neutron diffraction locates A-site Li in a distorted tetrahedron displaced from the conventional perovskite A-site, which differs considerably from the sites occupied by Li in the well studied La2/3-xLi3xTiO3 family. This is confirmed by the observation of a lower coordinated Li+ ion in the 6Li magic angle spinning nuclear magnetic resonance (NMR) spectra, in addition to the B-site LiO6, and supported computationally by density functional theory (DFT), which also suggests local order of A-site La3+ and Li+. DFT shows that the vacancies necessary for transport can arise from Frenkel or La excess defects, with an energetic cost of ~0.4 eV/vacancy in both cases. Ab initio molecular dynamics establishes that the Li+ ion dynamics occur by a pathway involving a series of multiple localised Li hops between two neighbouring A-sites with an overall energy barrier of ~0.25 eV, with additional possible pathways involving Li exchange between the A- and B-sites. A similar activation energy for Li+ ion mobility (~0.3 eV) was obtained from variable temperature 6Li and 7Li line narrowing and relaxometry NMR experiments, suggesting that the barrier to Li hopping between sites in La3Li3W2O12 is comparable to the best oxide Li+ ion conductors. AC impedance-derived conductivities confirm that Li+ ions are mobile but that the long-range Li+ diffusion has a higher barrier (~0.5 eV) which may be associated with blocking of transport by A-site La3+ ions.
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Sep 2016
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B18-Core EXAFS
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Thomas
Bennett
,
Yuanzheng
Yue
,
Peng
Li
,
Ang
Qiao
,
Haizheng
Tao
,
Neville
Greaves
,
Tom
Richards
,
Giulio
Lampronti
,
Simon
Redfern
,
Frédéric
Blanc
,
Omar K.
Farha
,
Joseph T.
Hupp
,
Anthony K.
Cheetham
,
David
Keen
Diamond Proposal Number(s):
[14249]
Abstract: Crystalline solids dominate the field of metal-organic frameworks (MOFs), with access to the liquid and glass states of
matter usually prohibited by relatively low temperatures of thermal decomposition. In this work, we give due consideration
to framework chemistry and topology to expand the phenomenon of the melting of three-dimensional MOFs, linking
crystal chemistry to framework melting temperature and kinetic fragility of the glass-forming liquids. Here we show that
melting temperatures can be lowered by altering the chemistry of the crystalline MOF state, which provides a route to
facilitate the melting of other MOFs. The glasses formed upon vitrification are chemically and structurally distinct from
the three other existing categories of melt-quenched glasses (inorganic non-metallic, organic and metallic), and retain the
basic metal-ligand connectivity of crystalline MOFs, which connects their mechanical properties to starting chemical
composition. The transfer of functionality from crystal to glass points towards new routes to tunable, functional hybrid
glasses.
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Feb 2016
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