Publications
26 results found
Nearchou A, Cornelius M-LU, Skelton JM, et al., 2019, Intrinsic flexibility of the EMT zeolite framework under pressure, Materials, Vol: 24, ISSN: 1420-3049
The roles of organic additives in the assembly and crystallisation of zeolites are still not fully understood. This is important when attempting to prepare novel frameworks to produce new zeolites. We consider 18-crown-6 ether (18C6) as an additive, which has previously been shown to differentiate between the zeolite EMC-2 (EMT) and faujasite (FAU) frameworks. However, it is unclear whether this distinction is dictated by influences on the metastable free-energy landscape or geometric templating. Using high-pressure synchrotron X-ray diffraction, we have observed that the presence of 18C6 does not impact the EMT framework flexibility—agreeing with our previous geometric simulations and suggesting that 18C6 does not behave as a geometric template. This was further studied by computational modelling using solid-state density-functional theory and lattice dynamics calculations. It is shown that the lattice energy of FAU is lower than EMT, but is strongly impacted by the presence of solvent/guest molecules in the framework. Furthermore, the EMT topology possesses a greater vibrational entropy and is stabilised by free energy at a finite temperature. Overall, these findings demonstrate that the role of the 18C6 additive is to influence the free energy of crystallisation to assemble the EMT framework as opposed to FAU.
Boström HLB, Collings IE, Cairns AB, et al., 2019, High-pressure behaviour of Prussian blue analogues: interplay of hydration, Jahn-Teller distortions and vacancies, Dalton Transactions, Vol: 48, Pages: 1647-1655, ISSN: 1477-9234
We report a high-pressure crystallographic study of four hydrated Prussian blue analogues: M[Pt(CN)6] and M[Co(CN)6]0.67 (M = Mn2+, Cu2+) in the range 0-3 GPa. Mn[Co(CN)6]0.67 was studied by single-crystal X-ray diffraction, whereas the other systems were only available in polycrystalline form. The Mn-containing compounds undergo pressure-induced phase transitions from Fm3[combining macron]m to R3[combining macron] at ∼1.0-1.5 GPa driven by cooperative tilting of the octahedral units. No phase transition was found for the orbitally disordered Cu[Co(CN)6]0.67 up to 3 GPa. Mn[Co(CN)6]0.67 is significantly softer than the other samples, with a bulk modulus of ∼14 GPa compared to ∼35 GPa of the powdered samples. The discrepant pressure responses are discussed in terms of the presence of structural defects, Jahn-Teller distortions, and hydration. The implications for the development of polar systems are reviewed based upon our high-pressure study.
Scelta D, Baldassarre A, Serrano-Ruiz M, et al., 2018, The p-sc structure in phosphorus: bringing order to the high pressure phases of group 15 elements, CHEMICAL COMMUNICATIONS, Vol: 54, ISSN: 1359-7345
Nobrega MM, Teixeira-Neto E, Cairns AB, et al., 2018, One-dimensional diamondoid polyaniline-like nanothreads from compressed crystal aniline, Chemical Science, Vol: 9, Pages: 254-260, ISSN: 2041-6520
© The Royal Society of Chemistry 2018. Low-dimensional nanomaterials such as highly ordered polyaniline (PANI) have attracted considerable interest due to their expected extraordinary electronic and optoelectronic properties. In spite of several attempts, the attainment of atomically well-ordered PANI is a long-standing challenge. Pressure-induced polymerization of aromatic molecules in the crystal phase has been demonstrated as a practicable route for the synthesis of highly ordered polymers but this approach has never been tested to produce PANI. Here we show the synthesis of diamondoid polyaniline-like nanothreads at 33 GPa and 550 K by compressing aniline in crystal phase-II. Infrared spectroscopy, transmission electron microscopy, X-ray diffraction data, and DFT calculations support the formation of this totally new polyaniline-like nanothread. The NH2-enriched carbon nanothread combines the outstanding mechanical properties of carbon nanotubes with the versatility of NH2 groups decorating the exterior of the nanothreads representing potential active sites for doping and as linkers for molecules with biological interest and inorganic nanostructures. The synergy of all of these properties emphasizes the strong potential of this material to be applied in a broad range of areas, from chemistry to materials engineering.
Gupta MK, Singh B, Mittal R, et al., 2017, Anomalous thermal expansion, negative linear compressibility, and high-pressure phase transition in ZnAu2(CN)4: Neutron inelastic scattering and lattice dynamics studies, Physical Review B, Vol: 96, ISSN: 2469-9950
© 2017 American Physical Society. We present temperature-dependent inelastic-neutron-scattering measurements, accompanied by ab initio calculations of the phonon spectra and elastic properties as a function of pressure to quantitatively explain an unusual combination of negative thermal expansion and negative linear compressibility behavior of ZnAu2(CN)4. The mechanism of the negative thermal expansion is identified in terms of specific anharmonic phonon modes that involve bending of the -Zn-NC-Au-CN-Zn- linkage. The soft phonon at the L point at the Brillouin zone boundary quantitatively relates to the high-pressure phase transition at about 2 GPa. The ambient pressure structure is also found to be close to an elastic instability that leads to a weakly first-order transition.
Scelta D, Baldassarre A, Serrano-Ruiz M, et al., 2017, Interlayer Bond Formation in Black Phosphorus at High Pressure., Angewandte Chemie International Edition, Vol: 56, Pages: 14135-14140, ISSN: 1521-3757
Black phosphorus was compressed at room temperature across the A17, A7 and simple-cubic phases up to 30 GPa, using a diamond anvil cell and He as pressure transmitting medium. Synchrotron X-ray diffraction showed the persistence of two previously unreported peaks related to the A7 structure in the pressure range of the simple-cubic phase. The Rietveld refinement of the data demonstrates the occurrence of a two-step mechanism for the A7 to simple-cubic phase transition, indicating the existence of an intermediate pseudo simple-cubic structure. From a chemical point of view this study represents a deep insight on the mechanism of interlayer bond formation during the transformation from the layered A7 to the non-layered simple-cubic phase of phosphorus, opening new perspectives for the design, synthesis and stabilization of phosphorene-based systems. As superconductivity is concerned, a new experimental evidence to explain the anomalous pressure behavior of Tc in phosphorus below 30 GPa is provided.
Scelta D, Baldassarre A, Serrano-Ruiz M, et al., 2017, Interlayer Bond Formation in Black Phosphorus at High Pressure, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 56, Pages: 14135-14140, ISSN: 1433-7851
Dziubek K, Citroni M, Fanetti S, et al., 2017, Synthesis of High-Quality Crystalline Carbon Nitride Oxide by Selectively Driving the High-Temperature Instability of Urea with Pressure, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 121, Pages: 19872-19879, ISSN: 1932-7447
Dziubek K, Citroni M, Fanetti S, et al., 2017, High-Pressure High-Temperature Structural Properties of Urea, Journal of Physical Chemistry C, Vol: 121, Pages: 2380-2387, ISSN: 1932-7447
Angle-dispersive X-ray diffraction and Fourier transform infrared spectroscopy have been employed to study the phase diagram of urea crystal beyond 15 GPa and at temperatures in excess of 400 K. Previously reported Bridgman phase II was structurally characterized for the first time, and it is discovered that it coincides with room-temperature phase IV. Large metastability P–T regions were identified for all phases in the sequence I–III–IV–V, ascribed to the difficulty to disrupt the H-bonding network, a prerequisite to accomplish the molecular rearrangement necessary for the structural transformation. High-temperature studies and use of a hydrostatic compression medium allows the thermodynamic boundaries of phase III, and partly of phase IV, to be identified therefore making a considerable step forward in the knowledge of the phase diagram of urea.
Overy AR, Cairns AB, Cliffe MJ, et al., 2016, Design of crystal-like aperiodic solids with selective disorder–phonon coupling, Nature Communications, Vol: 7
Cairns AB, Cliffe MJ, Paddison JAM, et al., 2016, Encoding complexity within supramolecular analogues of frustrated magnets, NATURE CHEMISTRY, Vol: 8, Pages: 442-447, ISSN: 1755-4330
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- Citations: 15
Adamson J, Lucas TC, Cairns AB, et al., 2015, Competing hydrostatic compression mechanisms in nickel cyanide, PHYSICA B-CONDENSED MATTER, Vol: 479, Pages: 35-40, ISSN: 0921-4526
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- Citations: 3
Baxter EF, Bennett TD, Cairns AB, et al., 2015, A comparison of the amorphization of zeolitic imidazolate frameworks (ZIFs) and aluminosilicate zeolites by ball-milling, Dalton Transactions, Vol: 45, Pages: 4258-4268, ISSN: 1477-9234
X-ray diffraction has been used to investigate the kinetics of amorphization through ball-milling at 20 Hz, for five zeolitic imidazolate frameworks (ZIFs) – ZIF-8, ZIF-4, ZIF-zni, BIF-1-Li and CdIF-1. We find that the rates of amorphization for the zinc-containing ZIFs increase with increasing solvent accessible volume (SAV) in the sequence ZIF-8 > ZIF-4 > ZIF-zni. The Li–B analogue of the dense ZIF-zni amorphizes more slowly than the corresponding zinc phase, with the behaviour showing a correlation with their relative bulk moduli and SAVs. The cadmium analogue of ZIF-8 (CdIF-1) amorphizes more rapidly than the zinc counterpart, which we ascribe primarily to its relatively weak M–N bonds as well as the higher SAV. The results for the ZIFs are compared to three classical zeolites – Na-X, Na-Y and ZSM-5 – with these taking up to four times longer to amorphize. The presence of adsorbed solvent in the pores is found to render both ZIF and zeolite frameworks more resistant to amorphization. X-ray total scattering measurements show that amorphous ZIF-zni is structurally indistinguishable from amorphous ZIF-4 with both structures retaining the same short-range order that is present in their crystalline precursors. By contrast, both X-ray total scattering measurements and 113Cd NMR measurements point to changes in the local environment of amorphous CdIF-1 compared with its crystalline CdIF-1 precursor.
Collings IE, Hill JA, Cairns AB, et al., 2015, Compositional dependence of anomalous thermal expansion in perovskite-like ABX(3) formates, Dalton Transactions, Vol: 45, Pages: 4169-4178, ISSN: 1477-9234
The compositional dependence of thermal expansion behaviour in 19 different perovskite-like metal–organic frameworks (MOFs) of composition [AI][MII(HCOO)3] (A = alkylammonium cation; M = octahedrally-coordinated divalent metal) is studied using variable-temperature X-ray powder diffraction measurements. While all systems show essentially the same type of thermomechanical response—irrespective of their particular structural details—the magnitude of this response is shown to be a function of AI and MII cation radii, as well as the molecular anisotropy of AI. Flexibility is maximised for large MII and small AI, while the shape of AI has implications for the direction of framework hingeing.
Paddison JAM, Cairns AB, Khalyavin DD, et al., 2015, Nature of Partial Magnetic Order in the Frustrated Antiferromagnet Gd₂Ti₂O₇
The frustrated pyrochlore antiferromagnet Gd$_{2}$Ti$_{2}$O$_{7}$ has anunusual partially-ordered magnetic structure at the lowest measurabletemperatures. This structure is currently believed to involve four magneticpropagation vectors $\mathbf{k}\in \langle \frac{1}{2} \frac{1}{2} \frac{1}{2}\rangle^*$ in a cubic 4-$\mathbf{k}$ structure, based on analysis of magneticdiffuse-scattering data [J. Phys.: Condens. Matter 16, L321 (2004)]. Here, wepresent three pieces of evidence against the 4-$\mathbf{k}$ structure. First,we report single-crystal neutron-diffraction measurements as a function ofapplied magnetic field, which are consistent with the selective field-inducedpopulation of non-cubic magnetic domains. Second, we present evidence fromhigh-resolution powder neutron-diffraction measurements that rhombohedralstrains exist within magnetic domains, which may be generated bymagneto-elastic coupling only for the alternative 1-$\mathbf{k}$ structure.Finally, we show that the argument previously used to rule out the1-$\mathbf{k}$ structure is flawed, and demonstrate that magneticdiffuse-scattering data can actually be fitted quantitatively by a1-$\mathbf{k}$ structure in which spin fluctuations on ordered and disorderedmagnetic sites are strongly coupled. Our results provide an experimentalfoundation on which to base theoretical descriptions of partially-orderedstates.
Cairns AB, Goodwin AL, 2015, Negative linear compressibility, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 17, Pages: 20449-20465, ISSN: 1463-9076
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- Citations: 65
Hunt SJ, Cliffe MJ, Hill JA, et al., 2015, Flexibility transition and guest-driven reconstruction in a ferroelastic metal-organic framework, CRYSTENGCOMM, Vol: 17, Pages: 361-369, ISSN: 1466-8033
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- Citations: 17
Hill JA, Cairns AB, Lim JJK, et al., 2015, Zero-strain reductive intercalation in a molecular framework, CRYSTENGCOMM, Vol: 17, Pages: 2925-2928, ISSN: 1466-8033
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- Citations: 4
Tominaka S, Hamoudi H, Suga T, et al., 2015, Topochemical conversion of a dense metal-organic framework from a crystalline insulator to an amorphous semiconductor, CHEMICAL SCIENCE, Vol: 6, Pages: 1465-1473, ISSN: 2041-6520
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- Citations: 29
Cairns A, Goodwin A, 2014, Designing next-generation negative compressibility materials., Acta Crystallographica Section A Foundations and Advances, Vol: 70, Pages: C262-C262
<jats:p>Negative compressibility is a rare but desirable property whereby a material's crystal structure actually expands in one (negative linear compressibility, NLC) or two (negative area compressibility, NAC) principal directions against application of increasing hydrostatic pressure. The performance of such materials–for use in, for e.g., sensitive interferometric or ferroelectric pressure sensing devices, advanced actuators, or prototype artificial muscle–critically depends on the magnitude of intrinsic negative response. NLC and NAC have been previously reported in a diverse range of materials: from the elemental forms of selenium and tellurium, to transition metal oxides, halides and chalcogenides [1], to more recent reports of NLC in molecular materials, and metal–organic and metal–cyanide frameworks. We explore, using examples from our work [2,3] as well as that of others, how understanding known NLC and NAC materials can inform material design, and how the versatile chemistry of molecular frameworks–the connecting of cationic metal nodes with anionic molecular linkers in one or more dimensions–allows for the targeting, enhancing and coupling of functionalities. By analysis of the negative response across all known NLC and NAC materials we develop new understanding into the underlying mechanisms of these unusual responses. Structural motifs identified point towards strategies for designing the next-generation of these materials, including the simple "wine-rack," "honeycomb" and "spring" mechanisms, where hinging about nodes requires volume reduction by simultaneous expansion and contraction in perpendicular directions (Figure 1). We discuss the first report of "giant" NLC in zinc(II) dicyanoaurate(I), Zn[Au(CN)<jats:sub>2</jats:sub>]<jats:sub>2</jats:sub>, where the crystal structure expands >10% over 1.8 GPa [2], the unprecedented prolonged NAC
Hodgson SA, Adamson J, Hunt SJ, et al., 2014, Negative area compressibility in silver(I) tricyanomethanide, CHEMICAL COMMUNICATIONS, Vol: 50, Pages: 5264-5266, ISSN: 1359-7345
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- Citations: 37
Hermet P, Catafesta J, Bantignies J-L, et al., 2013, Vibrational and Thermal Properties of Ag-3[Co(CN)(6)] from FirstPrinciples Calculations and Infrared Spectroscopy, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 117, Pages: 12848-12857, ISSN: 1932-7447
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- Citations: 17
Collings IE, Cairns AB, Thompson AL, et al., 2013, Homologous Critical Behavior in the Molecular Frameworks Zn(CN)(2) and Cd(imidazolate)(2), JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 135, Pages: 7610-7620, ISSN: 0002-7863
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- Citations: 56
Cairns AB, Catafesta J, Levelut C, et al., 2013, Giant negative linear compressibility in zinc dicyanoaurate, NATURE MATERIALS, Vol: 12, Pages: 212-216, ISSN: 1476-1122
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- Citations: 115
Cairns AB, Goodwin AL, 2013, Structural disorder in molecular framework materials, CHEMICAL SOCIETY REVIEWS, Vol: 42, Pages: 4881-4893, ISSN: 0306-0012
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- Citations: 78
Cairns AB, Thompson AL, Tucker MG, et al., 2012, Rational Design of Materials with Extreme Negative Compressibility: Selective Soft-Mode Frustration in KMn[Ag(CN)(2)](3), JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 134, Pages: 4454-4456, ISSN: 0002-7863
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- Citations: 74
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