The short range order of incommensurate structures of Li adsorbed on Cu(100) is discussed. According to the LEED measurements, the Li atoms form linear incommensurate chains pretty well ordered in the missing rows induced by the Li adsorption and the short range order between the Li atom chains is weaker. A one-dimensional classical XY-model is proposed for this system where the pretty well ordered linear chain is represented by a spin and the nearest neighbor spins couple. This model can be easily solved and the results are in satisfactory agreement with the experimental ones.
