Pressure-Driven Commensurate-Incommensurate Transition Low-Temperature Submonolayer Krypton on Graphite

By using D2 gas as a source of two-dimensional spreading pressure, we have studied the commensurate-incommensurate (C-I) transition in submonolayer Kr on ZYX graphite at temperatures near 40 K. High-resolution synchrotron x-ray diffraction results show both hysteresis and C-I phase coexistence, clear signatures of a first-order transition.

This agrees with theoretical predictions, but apparently gives different behavior from earlier studies at higher temperatures and coverages.