Melting of potassium to 22 GPa

Using in-situ x-ray diffraction, the melting curve of potassium was determined to 22 GPa and was found to be remarkably similar to that of sodium, and strikingly different to that reported previously. The existence of a maximum in the bcc phase was determined at 5.8(5) GPa and 530(10) K; the melting temperature was then observed to decrease over several GPa, flattening out at the bcc-fcc-liquid triple point at 13.6(3) GPa and 466(10) K, before further decreasing from 15.6(3) GPa to a minimum at 19(1) GPa and 390(10) K. It then regained a positive slope and increased rapidly at a rate of 65(5) K/GPa In the tI19 phase it was observed that the guest chains "melted" before the host structure at 20.3(3) GPa and 420(10) K, but were solid at 22.5(3) GPa and 350(10) K.