Phase diagram of hydrogen adsorbed on Ni(111)

An explanation for the phase diagram of the H/Ni(111) system is proposed, where the existence of the p(2 × 2) phase is assumed in addition to the (2 × 2) phase. Using the position-space renormalization-group theory with prefacing transformation, a lattice gas on a honeycomb lattice, including up to 6th nearest neighbor interactions, is treated. Another explanation previously put forward by Domany et al. is also examined, where the occurrence of the (2 × 2) ordered phase and the gas + p(2 × 2) coexistence phase is assumed. The phase diagrams thus obtained for these two cases are exhibited and discussed.