Evidence for Discommensurations in Graphite Intercalation Compounds

Abstract

New x-ray diffuse scattering results are presented that show that the layer structure in stage-2 alkali-metal graphite intercalation compounds is almost commensurate with a $(\sqrt{7}\ifmmode\times\else\texttimes\fi{}\sqrt{7})R19.11\ifmmode^\circ\else\textdegree\fi{}$ superlattice. Through model calculations, features of the in-plane diffraction patterns are associated with a hexagonal array of discommensurations oriented parallel to the real-space graphite [110] directions. The array appears to be disordered down to at least $T=10$ K. Several previously unexplained results are understood through our model.