New type of pressure-induced phase transition in potassium graphite intercalation compounds Original Research Article

New stage 1 potassium-graphite intercalation compound was recently reported. This compound differs from those already known by its structure, which includes two metal layers in the same gallery. It has roughly KC4 stoichiometry. This compound was studied under high quasi-hydrostatic pressures up to 25 kbar. From the volume vs pressure measurements and X-ray diffraction studies, it follows that under high pressure the sample overgoes first-order phase transition accompanied by the formation of dense single layers of potassium with the same (KC4) stoichiometry. The compound with such a structure and stoichiometry was known before, but it was obtained by the direct high-pressure synthesis from metal and graphite, and is not observable at ambient conditions.