SCD - Single Crystal Diffractometer
Instrument Scientist - Arthur J. Schultz
Scientific Associate - Martha E. Miller
Post Doc - Paula Briggs-Piccoli
Software and Procedures
| Initial Flight Path |
950 cm |
| Sample-to-Detector Distance |
|
| Detector 1 |
23 cm |
| Detector 2 |
18 cm |
| Detector Type |
Position-Sensitive Scintillator |
| Detector Angle |
|
| Detector 1 |
Centered at 2q = 75° |
| Detector 2 |
Centered at 2q = 120° |
| Detector Positional Resolution |
1.5 mm |
| Beam Size |
6-12 mm |
| D-spacing Range |
0.36.5 Å |
| Wave-Vector Resolution |
2% @ 90° |
Sample Environments
| Hot-Staged Displex |
4-900 K |
| Displex Closed Cycle Helium Refrigerator |
12473 K |
| Heli-Tran Liquid Helium Transfer Refrigerator |
2300 K |
| Furnaces |
3001000 K |
| Helium Pressure Cell Mounted on Displex |
05 kbar @ 12300 K |
The IPNS Single Crystal Diffractometer (SCD) is based on the time-of-flight (TOF) Laue technique which combines the use of a large-area position-sensitive detector (PSD) with a range of incident neutron wavelengths available from a pulsed neutron source. With a stationary sample and detector, a three-dimensional sampling of reciprocal space is obtained that may contain hundreds of Bragg reflections. In addition, all of reciprocal space between the peaks is also measured simultaneously making this technique highly advantageous for studying pressure and temperature dependent phase transitions. Some examples of types of studies carried out on the SCD include: the structures of transition metal complexes containing hydrides or CHmetal interactions; the pressure-dependence of the modulated structure of an organic superconductor; the magnetic form factor of a high-Tc related compound; the pressure-dependence of a switchable Jahn-Teller distortion.
In one SCD experiment, a crystal of oxygen rich La2CuO4+d, which is a superconductor with Tc = 40 K for d » 0.1, was studied. The crystal was prepared by room temperature electrochemical oxidation of La2CuO4 and appeared to be single phase with Fmmm symmetry and with the excess oxygen located between adjacent LaO layers from analysis of the fundamental Bragg peaks. In addition, satellites arising from a modulation could be clearly identified in the single-crystal data, as shown in the figure. The satellites are indicative of a superlattice due to ordering of the interstitial oxygen atoms and of the apical oxygen displacements. [P. G. Radaelli et al., Phys. Rev. B 48, 499 (1993)]
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