Neutron diffraction of potassium-graphite intercalation compounds at high pressure: Staging transitions and one-dimensional disorder.

Detailed (00L) neutron scattering profiles have been measured versus hydrostatic pressure (0 P 20 kbar) at room temperature for a series of potassium-graphite intercalation compounds KC(x) with 8 x 40. In all cases the average density of filled galleries along the c-axis decreases with increasing P, implying a concomitant increase in the (average) areal K density within a gallery. For various x values we observe both large P regions exhibiting continuous evolution of different stages, and narrow P regions where the average stage changes abruptly. Least squares fits over extended q ranges encompassing many reflections have been performed, based upon the Hendricks- Teller model of one-dimensional disorder.