In-Plane Density of Potassium Liquid and Liquid-Solid Transitions in Potassium Graphite Intercalation Compounds

An x-ray-diffraction study of in-plane structures in K-graphite has revealed a remarkable chemical potential (${\mu }_{\mathrm{K}}$) dependence of the in-plane density in pure stages 1 and 2, and some continuous nature of the stage-1 melting transition. A simultaneous growth of intralayer and interlayer correlations of K atoms in stage-1 liquid is observed as ${\mu }_{\mathrm{K}}$ approaches the solidification poínt. This transition is weakly first order. A new stacking transition from $\alpha \beta$ to $\alpha \beta \gamma \delta$ K layers in stage-1 solid is also reported.