Commensurate Structures of Adatoms on a Square Lattice

Abstract

We propose a phenomenological lattice gas model to investigate an adsorbed system with strong interaction between adatoms and the substrate. In our model, adatoms sit on top of substrate atoms of the square lattice and adsorption induces surface reconstructions. The ground state of this system is discussed and is shown to have many commensurate phases of obliquely striped structure of adatoms. It is shown that these structures are caused by the long range effective adatom-adatom interaction mediated by the displacements of substrate atoms. A complex ground state phase diagram is also given.