Elastic neutron scattering studies of the structure of graphite intercalated with potassium and ammonia

Abstract

We have measured the in-plane and c-axis elastic neutron scattering from the ternary potassium-ammonia-graphite intercalation compound K(${\mathrm{ND}}_3$ ${)}_{4.3}$ ${\mathrm{C}}_{24}$ at room temperature. The c-axis scans establish that the graphite layers stack in an eclipsed configuration and that there is no correlation between the intercalant layers. The in-plane diffuse scattering from the intercalant layers is well accounted for by a computer-generated structural model in which each potassium ion is symmetrically four-fold coordinated to ammonia molecules to form closely packed, five-membered clusters. This model had been previously applied to explain the in-plane diffuse x-ray scattering results from K(${\mathrm{NH}}_3$ ${)}_{4.38}$ ${\mathrm{C}}_{24}$. Discrepancies between the calculated and measured diffraction patterns are attributed to a relaxation of the four-fold symmetry of the K-${\mathrm{ND}}_3$ clusters.