565 research outputs found

    Nanostructure determination from the pair distribution function: A parametric study of the INVERT approach

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    We present a detailed study of the mechanism by which the INVERT method [Phys. Rev. Lett. 104, 125501] guides structure refinement of disordered materials. We present a number of different possible implementations of the central algorithm and explore the question of algorithm weighting. Our analysis includes quantification of the relative contributions of variance and fit-to-data terms during structure refinement, which leads us to study the roles of density fluctuations and configurational jamming in the RMC fitting process. We present a parametric study of the pair distribution function solution space for C60, a-Si and a-SiO2, which serves to highlight the difficulties faced in developing a transferable weighting scheme.Comment: 15 pages, 7 figures, formatted for JPCM (RMC issue

    The role of adult education in the development of E. Africa

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    Structure determination of disordered materials from diffraction data

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    We show that the information gained in spectroscopic experiments regarding the number and distribution of atomic environments can be used as a valuable constraint in the refinement of the atomic-scale structures of nanostructured or amorphous materials from pair distribution function (PDF) data. We illustrate the effectiveness of this approach for three paradigmatic disordered systems: molecular C60, a-Si, and a-SiO2 . Much improved atomistic models are attained in each case without any a-priori assumptions regarding coordination number or local geometry. We propose that this approach may form the basis for a generalised methodology for structure "solution" from PDF data applicable to network, nanostructured and molecular systems alike.Comment: 4 pages, 3 figures, set out as for PR

    Defect-dependent colossal negative thermal expansion in UiO-66(Hf) metal-organic framework

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    Thermally-densified hafnium terephthalate UiO-66(Hf) is shown to exhibit the strongest isotropic negative thermal expansion (NTE) effect yet reported for a metal-organic framework (MOF). Incorporation of correlated vacancy defects within the framework affects both the extent of thermal densification and the magnitude of NTE observed in the densified product. We thus demonstrate that defect inclusion can be used to tune systematically the physical behaviour of a MOF.Comment: 8 pages, 4 figures, revise

    Gendered experiences of academic staff in relation to research activity and the REF2014

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    This report is based on research commissioned by the institutional Research and Knowledge Transfer Office between June 2015 and June 2016. This research has focused on generating qualitative and quantitative data as to the potential reasons why there appears to be a gender disparity in research productivity within the commissioning institution. In particular, the number of women self-selecting for representation in the REF2014 was comparatively low. This research was led by Dr Chantal Davies (as part of her broader remit in relation to the Forum for Research into Equality and Diversity) with Dr Ruth Healey as co-researcher and Anthony Cliffe as research assistant. A Steering Group made up of representatives from across the institution oversaw the process
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