TheFdddfour-circle diffractometer for single-crystal X-ray studies at temperatures down to 9 K

Abstract

The Fddd four-circle diffractometer system has been developed to perform X-ray diffraction experiments at temperatures as low as 9 K. The diffractometer consists of: (i) a Siemens rotatinganode generator; (ii) a Huber goniometer with offset X circle; (iii) a Siemens Fast Scintillation Detector; and (iv) an APD '202' Displex cryogenic refrigerator. The belt-driven rotating anode gives an X-ray flux that is far in excess of that obtained from a sealed X-ray tube and leads to faster data collections and the opportunity to study smaller samples. X-ray beam alignment requires precise movements of the 300 kg goniometer and this is achieved using compressed air pads. Steel-braided gas lines that allow the transfer of helium gas between the Displex and the compressor are supported by a counterbalance system. The stress on these lines has been reduced by attaching them to the Displex via high-pressure rotating joints and by passing them through a metal ring that is attached to the Z circle. A compact vacuum gauge has been mounted through one of the four ports on the top of the cryostat and gives valuable information on the pressure within the Displex sample chamber during an experiment. Crystals are mounted on sharpened 0.3 mm graphite pencil leads that are held in a newly designed sample mount. The temperature reported from the second stage of the Displex has been assessed by consideration of temperature standards that include the solid-state phase transitions of benzil (1,2-diphenylethanedione) and terbium vanadate.

Studying the Origin of the Antiferromagnetic to Spin‐Canting Transition in the β‐p‐NCC6F4CNSSN.Molecular Magnet

“…X‐ray crystallography : Single‐crystal X‐ray diffraction data were collected at 12 K on the Fddd diffractometer33 equipped with a Displex cryo‐refrigerator. Data were obtained up to 60° in 2 θ by using graphite monochromated Mo Kα radiation ( λ =0.71073 Å) from a needle‐shaped black single crystal (0.02×0.02×0.10 mm).…”

A Thermal Spin Transition in [Co(bpy)3][LiCr(ox)3] (ox=C2O42−; bpy=2,2′-bipyridine)

“…Single crystals in the form of perfect tetrahedra with edges of up to 0.4 mm were grown by slow diffusion in a silicate gel. [22] X-ray diffraction studies: The relevant structure determination parameters are given in Table 1 [23] which consists of an APD 202 Displex cryogenic refrigerator on a Huber 512 goniometer with an offset c-circle, a Bruker Mo rotating anode generator (l 0.71073 ) and a fast scintillation detector. A dark red crystal was attached to a sharpened graphite rod (0.3 mm) by means of a lowtemperature epoxy glue and was mounted on the Displex.…”

The XIPHOS diffraction facility for extreme sample conditions

“…(h) A redesigned sample mount. To enhance cooling times and equilibration of the measured temperature compared with that at the sample position, the sample mount has been modified from that used previously by Copley et al (1997). The principal change has been to reduce the volume of material being cooled between the diode, where the temperature measurement is carried out, and the sample position.…”

“…All structural phase transitions were monitored, allowing an equilibration time of at least 10 min at each data point before the crystal centring was checked and data recorded. The crystals were all mounted as described by Copley et al (1997) on sharpened 0.5 mm graphite rods using a low-temperature epoxy resin (Oxford Instruments, TRZ0004). The calibration experiments showed that the temperature interpreted from the Lakeshore diode was accurate to within 0.5 K with a nominal stability of < 0.1 K.…”

“…XIPHOS fits neatly into the niche between conventional home diffractometers and their central facility counterparts. A complete rebuild was performed, rather than an upgrade of the previously constructed Fddd diffractometer (Copley et al, 1997), to take advantage of the significant developments of both detectors and generators in the field of SCD.…”