Spatial distribution of composition and misfit dislocations on the surface of alloys
The Frenkel - Kontorova theory of phase transitions into an incommensurate phase with the formation of a superlattice of misfit dislocations on a surface is extended to the case of alloys for which the lattice mismatch depends on the local composition. A model is considered that takes into account the possibility of atomic diffusion between the surface and the bulk. Peculiarities of the conditions at the surface are accounted for by introducing a chemical potential for one type of the atoms of the alloy which leads to a difference in composition between the bulk and the surface layer. We calculated the average mismatch between the surface and the bulk lattices and the critical value of chemical potential at which the phase transition into an incommensurate phase with misfit dislocations occurs. A phase diagram of the system in coordinates of temperature and chemical potential is presented for the alloy .