Crystal structure of Y3Cu9(OH)19Cl8 at high pressure and low temperature

Within this project we investigate structural details of the distorted kagome system Y3Cu9(OH)19Cl8 at high pressures and low temperatures by single crystal x-ray diffraction. Data are from three different beamtimes, IH-HC-3747 (ID27), IH-HC-4021 (ID27) and BLC15473 (ID15B). Dataset names contain information on pressure and temperature. The diffraction geometry was calibrated by measurements on a vanadinite single crystal and CeO2 powder. The sample was a plate-like single crystal of Y3Cu9(OH)19Cl8 with dimensions of approximate 50x50x20 microns^3, embedded in a diamond anvil cell for measurements on ID27 and mounted with vacuum grease on a 300 microns thick diamond plate for measurements at ID15B. Single crystal XRD data under applied pressure at all temperatures were collected at the beamline ID27 and the low temperature data at ambient pressure at ID15B. We used membrane driven diamond anvil cells and helium as the pressure transmitting medium. Natural single crystalline diamonds with Boehler-Almax cut culets of 500 μm in size were mounted on seats with a modified Boehler-Almax design and an opening of 70 degrees. Stainless steel was used as gasket material. 200 μm thick plates were pre-indented to 100 μm. The sample chamber was created by laser drilling a hole of 300 μm in diameter. The cell was loaded with compressed He and closed at 1400 bar. The applied pressure was determined from ruby fluorescence.
Room temperature data was collected in continuous φ rotation over 68◦ in shutterless readout of the EIGER2 X CdTe 9M detector (Dectris, Switzerland) in 0.25◦ steps. For the low temperature experiments diamond anvil cells made of CuNi2Be were mounted in a Helium flow cryostat and data collected in continuous φ rotation over 64 degrees. For the ambient pressure experiment at low temperature the sample was mounted on a 300μm thick diamond plate and cooled
with a small Helium flow cryostat. Data was collected in continuous φ rotation over 70◦ in 0.25◦ steps. The detector distance was calibrated using CeO2 powder to 185.5 mm for the room temperature data at ID27, 183.8 mm for low temperature at ID27 and 179.2 mm for low temperature at ID15B. The key experimental results were obtained using monochromatic X rays with a wavelength of 0.22290 Å for room temperature data, 0.3738 Å for low temperature at ID27 and 0.4099 Å for low temperature data at ID15B.