Browsing by Author "Martin, AV"

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    Crystal structure of protic ionic liquids and their hydrates
    (International Union of Crystallography, 2021-08-14) Hassett, MP; Brand, HEA; Binns, J; Martin, AV; Greaves, TL
    Protic Ionic Liquids (PILs) are a class of tailorable solvents made up of fused salts with melting points below 100 °C, which are formed through a Brønsted acid-base reaction involving proton exchange[1]. These solvents have applications as lubricants, electrolytes, and many other uses[2]. Although they are quite similar to molten salts, their crystal structures have not been explored in-depth, with only ethylammonium nitrate (EAN) having a reported crystal structure[3, 4]. Ten alkylammonium-based protic ionic liquids at both neat (<1 wt% water) and 90 mol% PIL, 10 mol% water concentrations were selected. Diffraction patterns were collected at the Australian Synchrotron ANSTO while attempting to crystallise the samples by cooling to 120 K. Five samples crystallised (3 neat, 2 dilute), where the temperature of the system was then increased at a rate of 6 K/min to room temperature. From these patterns we have identified a number of crystal phases, identifying their stability ranges and lattice constant variation from 120 K to room temperature. © 2021 The Authors
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    Measurements of long-range electronic correlations during femtosecond diffraction experiments performed on nanocrystals of Buckminsterfullerene
    (MyJove, 2017-08-22) Ryan, RA; Williams, S; Martin, AV; Dilanian, RA; Darmanin, C; Putkunz, CT; Wood, D; Streltsov, VA; Jones, MWM; Gaffney, N; Hofmann, F; Williams, GJ; Boutet, S; Messerschmidt, M; Seibert, M M; Curwood, EK; Balaur, E; Peele, AG; Nugent, KA; Quiney, HM; Abbey, B
    The precise details of the interaction of intense X-ray pulses with matter are a topic of intense interest to researchers attempting to interpret the results of femtosecond X-ray free electron laser (XFEL) experiments. An increasing number of experimental observations have shown that although nuclear motion can be negligible, given a short enough incident pulse duration, electronic motion cannot be ignored. The current and widely accepted models assume that although electrons undergo dynamics driven by interaction with the pulse, their motion could largely be considered 'random'. This would then allow the supposedly incoherent contribution from the electronic motion to be treated as a continuous background signal and thus ignored. The original aim of our experiment was to precisely measure the change in intensity of individual Bragg peaks, due to X-ray induced electronic damage in a model system, crystalline C60. Contrary to this expectation, we observed that at the highest X-ray intensities, the electron dynamics in C60 were in fact highly correlated, and over sufficiently long distances that the positions of the Bragg reflections are significantly altered. This paper describes in detail the methods and protocols used for these experiments, which were conducted both at the Linac Coherent Light Source (LCLS) and the Australian Synchrotron (AS) as well as the crystallographic approaches used to analyse the data. © 2017 Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported. .
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    Understanding order and correlation in liquid crystals by fluctuation scattering
    (Australian Nuclear Science and Technology Organisation, 2021-11-26) Binns, J; Adams, P; Kewish, CM; Greaves, TL; Martin, AV
    Characterising the supramolecular organisation of macromolecules in the presence of varying degrees of disorder remains one of the challenges of macromolecular research. Discotic liquid crystals (DLCs) are an ideal model system for understanding the role of disorder on multiple length scales. Consisting of rigid aromatic cores with flexible alkyl fringes, they can be considered as one-dimensional fluids along the stacking direction and they have attracted attention as molecular wires in organic electronic components and photovoltaic devices. With its roots in single-particle imaging, fluctuation x-ray scattering (FXS) is a method that breaks free of the requirement for periodic order. However, the interpretation of FXS data has been limited by difficulties in analysing intensity correlations in reciprocal space. Recent work has shown that these correlations can be translated into a three-and four-body distribution in real space called the pair-angle distribution function (PADF) – an extension of the familiar pair distribution function into a three-dimensional volume. The analytical power of this technique has already been demonstrated in studies of disordered porous carbons and self-assembled lipid phases. Here we report on the investigation of order-disorder transitions in liquid crystal materials utilising the PADF technique and the development of facilities for FXS measurements at the Australian Synchrotron. © 2021 The Authors