LEED study of the order-disorder transition of the p(2 × 2) phase of oxygen chemisorbed on Ni(111)

The order-disorder transition of the p(2 × 2) phase of oxygen chemisorbed on Ni(111) has been studied using low-energy electron diffraction (LEED). The transition was found to be continuous, and the measured critical exponents are consistent with those predicted for the 4-state Potts model. These results agree with the theoretical predictions for this overlayer based on symmetry considerations, but disagree with two other experimental studies. These discrepancies are discussed.