Poster Presentation The 35th Biennial Conference of the Society of Crystallographers in Australia and New Zealand 2024 (Crystal 35)

Keeping cool under pressure: the development of a low-temperature high-pressure diamond anvil cell for X-ray diffraction (#112)

Aston M Summers 1 , John Hitchings 1 , Stephanie Boer 2 , Rosemary Young 2 , Rachel Williamson 2 , Alan Riboldi-Tunnicliffe 2 , Stephen A Moggach 1
  1. The University of Western Australia, CRAWLEY, WA, Australia
  2. MX Beamlines, ANSTO Australian Synchrotron, Clayton, Victoria, Australia

Single-crystal X-ray diffraction (SC-XRD) experiments are almost always conducted at low-temperatures (~100 K) using an open-flow cryostat, yet most high-pressure SC-XRD experiments are performed at ambient temperature. Low temperatures allow for the collection of higher-quality data, primarily due to a reduction in thermal vibration and radiation damage,1 while enabling the exploration of phenomena that is dependent on both variations in temperature and pressure.2 Generally, concurrent low-temperature and high-pressure experiments are performed using helium fridges with sealed beryllium shrouds.3,4 This apparatus allows for cryogenic temperatures to be reached, however, these apparatus are generally bulky and expensive, requiring significant modification to the diffraction experiment.3

Here, we describe the development of a turnbuckle diamond anvil cell that can be mounted on a conventional goniometer head and cooled using an open-flow cryostat. The cell is similar in design to that constructed by Jin et al.,5 but distinguishes itself by being more accessible, requiring less specialised equipment to operate and can be manufactured by conventional machining methods.

Calibration of the internal temperature of the cell and the pressure changes in the system when cooled were performed by monitoring the contraction of the unit cell parameters of hexamethylenetetramine and the shift in the ruby fluorescence doublet. From this we determined that the minimum temperature accessible was 140 K when the cryostat was set to its minimum of 100 K. When cooled to 100 K at lower initial pressures (<1 GPa) the pressure dropped by ~0.10 GPa, when pressure was increased past 1 GPa it gradually started to increase in pressure by ~0.05 GPa when cooled to 140 K. The calibrated cell has been used at the Australian Synchrotron on the MX1 beamline to collect variable-temperature SC-XRD data at varying pressures on a variety of single-crystal molecular switches. The cell has proven to be very effective and offers a seamless integration with the current high-pressure set-up with little additional equipment required.

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  5. Jin, H., Woodall, C. H., Wang, X., Parsons, S. & Kamenev, K. V. A novel diamond anvil cell for x-ray diffraction at cryogenic temperatures manufactured by 3D printing. Rev Sci Instrum 88, (2017).