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Gould J.A.,University of Liverpool | Rosseinsky M.J.,University of Liverpool | Moggach S.A.,Center for Science at Extreme Conditions
Dalton Transactions | Year: 2012

Application of pressure on the Cu-complex CuAsp causes Jahn-Teller Cu-O bonds to be compressed, increasing the coordination environment from [4 + 1] to [4 + 2], highlighted by a discontinuity on compression of these bonding interactions. © 2012 The Royal Society of Chemistry. Source

McMahon M.I.,Center for Science at Extreme Conditions
Journal of Synchrotron Radiation | Year: 2014

The advent of the ESRF, APS and SPring-8 third-generation synchrotron sources in the mid-1990s heralded a golden age of high-pressure X-ray science. The high-energy monochromatic micro-focused X-ray beams from these storage rings, combined with the new high-pressure diffraction and spectroscopy techniques developed in the late 1980s, meant that researchers were immediately able to make detailed structural studies at pressures comparable with those at the centre of the Earth, studies that were simply not possible only five years previously. And new techniques, such as X-ray inelastic scattering and X-ray nuclear scattering, became possible at high pressure for the first time, providing wholly-new insight into the behaviour of materials at high densities. The arrival of new diffraction-limited storage rings, with their much greater brightness, and ability to achieve focal-spot diameters for high-energy X-ray beams of below 1μm, offers the possibility of a new generation of high-pressure science, both extending the scope of what is already possible, and also opening ways to wholly-new areas of investigation. © 2014 International Union of Crystallography. Source

Vale J.G.,University College London | Vale J.G.,Ecole Polytechnique Federale de Lausanne | Boseggia S.,University College London | Boseggia S.,Diamond Light Source | And 12 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

The magnetic critical scattering in Sr2IrO4 has been characterized using x-ray resonant magnetic scattering (XRMS) both below and above the three-dimensional antiferromagnetic ordering temperature TN. The order parameter critical exponent below TN is found to be β=0.195(4), in the range of the two-dimensional (2D) XYh4 universality class. Over an extended temperature range above TN, the amplitude and correlation length of the intrinsic critical fluctuations are well described by the 2D Heisenberg model with XY anisotropy. This contrasts with an earlier study of the critical scattering over a more limited range of temperature, which found agreement with the theory of the isotropic 2D Heisenberg quantum antiferromagnet, developed to describe the critical fluctuations of the conventional Mott insulator La2CuO4 and related systems. Our study therefore establishes the importance of XY anisotropy in the low-energy effective Hamiltonian of Sr2IrO4, the prototypical spin-orbit Mott insulator. © 2015 American Physical Society. ©2015 American Physical Society. Source

Gould J.A.,University of Liverpool | Rosseinsky M.J.,University of Liverpool | Warren J.E.,Daresbury Laboratory | Moggach S.A.,Center for Science at Extreme Conditions
Zeitschrift fur Kristallographie | Year: 2014

The hydrostatic compression of the chiral metal-organic framework [Ni(L-Asp)(H2O)2] · H2O (NiAsp-I) has been studied to 6.07 GPa by single crystal X-ray diffraction. Over the course of this pressure range the compound undergoes a phase transition between 0.58 GPa and 1.26 GPa, yielding NiAsp-II. Both polymorphs are orthorhombic, P2 12121, and feature 1D chains of Asp-Ni-Asp moieties. During the transition, the Ni(II) octahedra rotate, resulting in a dramatic shift in the position of the axial bonds with respect to the direction of polymer formation, and gives rise to an anisotropic compression of the unit cell dimensions. Source

Graham A.J.,Center for Science at Extreme Conditions | Tan J.-C.,University of Cambridge | Allan D.R.,Diamond Light Source | Moggach S.A.,Center for Science at Extreme Conditions
Chemical Communications | Year: 2012

Here we present detailed structural data on the effect of high pressure on Cu-btc. Application of pressure causes solvent to be squeezed into the pores until a phase transition occurs, driven by the sudden compression and expansion of equatorial and axial Cu-O bonds. © 2012 The Royal Society of Chemistry. Source

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