Phase diagram and phase transitions of krypton on graphite in the one-to-two-layer regime

We report a high-resolution x-ray diffraction study of the freezing transitions of krypton on graphite for coverages above one monolayer. For pressure $P>430$ Torr there is a single continuous incommensurate-fluid-to-incommensurate-solid freezing transition. For $P<430$ Torr the freezing at fixed pressure is doubly reentrant with the succession of phases fluid {→} commensurate solid {→} reentrant fluid {→} incommensurate solid. The first transition is of first order, whereas the other two are continuous within the experimental resolution.