O R D E R - D I S O R D E R TRANSITIONS IN LOW STAGE AsF 5 GRAPHITES
J. B. HASTINGS and C. R. FINCHER, Jr.
Physics Department, Brookhaven National Laboratory *, Upton, N Y 11973 (U.S.A.) M. MORAN and J. E. FISCHER
Moore School of Electrical Engineering and Laboratory for Research on the Structure of Matter, University of Pennsylvania**, Philadelphia, PA 19104 (U.S.A.)
Summary
X-ray scattering studies of low stage AsF5 graphites provide the first direct observations of the order-disorder transitions in these compounds. In CsAsF 5 the order parameter increases continuously to saturation over a broad range of temperature, in agreement with previous, indirect measurements. The low temperature structure in this compound does not appear to be the previously proposed 2a × 2a structure observed in the Stage 1 K and Cs compounds. Studies of the Stage 2 compound will also be presented and compared with the behavior for Stage 1.
*Work at Brookhaven National Laboratory supported by the Division of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC02-76CH00016. **Supported in part by NSF Division of Materials Science grant DMR 76-80994.