O/Rh(100) p(2x2)->c(2x2) order-disorder phase transition

An order-disorder transition of oxygen adsorbed on the Rh(100) surface has been studied by means of spot profile analysis low-energy electron diffraction (SPA-LEED). The p(2X2)-->c(2X2) transition has been found to belong to the Ising universality class, with critical temperature 450+/-5 K. Careful consideration of the profile broadening allows the determination of the type of defect implicated in the disordering process, and it is defined in terms of a surface Burgers vector. Furthermore, the thermodynamic parameters allow an energy/unit length to be associated with these defects.