We report the results of a combined extended x-ray-absorption fine structure (EXAFS) and x-ray diffraction study of Kr adsorbed on a ZYX graphite substrate. The data are consistent with simple models for atomic fluctuations, which are found to be surprisingly large. Thermal fluctuations weaken the Kr-Kr EXAFS signal, so that the average number of Kr neighbors and the EXAFS Debye-Waller factor cannot be determined independently. The disordered phase at the commensurate-incommensurate transition appears to have substantial local order in the Kr-C signal, consistent with the domain-wall description of that phase.

• Received 11 March 1987

DOI:https://doi.org/10.1103/PhysRevB.37.3461