Evidence for a Commensurate-Incommensurate Phase Transition with an Intermediate Fluid Phase:N2Adsorbed on Ni(110)

Abstract

Low-energy electron diffraction and thermodynamic measurements are reported for molecular nitrogen weakly chemisorbed on a Ni(110) surface in the temperature region between 87 and 150 K. A commensurate (2×1) phase transforms with increasing coverage into a sequence of smoothly varying incommensurate solid structures via a liquid-like intermediate phase. This is apparently the first experimental example of the commensurate-fluid-incommensurate phase sequence in uniaxial systems predicted by several recent theories.