Incommensurate surface phases in a model of reconstruction and roughening

An anisotropic solid-on-solid type model is introduced to attempt a unified description of both the surface reconstruction and roughening phase transitions. The low-temperature phase diagram of the model is investigated in detail via a domain-wall analysis revealing the presence of several incommensurate phases, separated by continuous phase transitions, for temperatures T between reconstruction, Tc, and roughening TR. True commensurate order develops only at T = 0, but a pseudo commensurate-incommensurate transition at Tc∗ > 0 marks the onset of thermal surface deconstruction. A high-temperature roughening transition of the Kosterlitz-Thouless type should terminate the sequence of incommensurate phases. The resulting phase diagram may apply to the description of systems such as noble metal [110] solid-vapour interface structures.