Molecular clustering in a two-dimensional metal-ammonia solution

We have measured the in-plane x-ray diffraction pattern of the two-component K+ -NH3 liquid layers in the ternary graphite intercalation compound K(NH3)4.33C24. The measured pattern is in semiquantitative agreement with the scattering calculated for a random distribution of coplanar hard K+ and NH3 disks, provided that the K+ ions are bound symmetrically to four NH3 molecules. We show that the K-NH3 layers constitute the two-dimensional structural analog of the well-known bulk three-dimensional K-NH3 metal-ammonia solutions. © 1985 The American Physical Society.