An exactly solvable microscopic model was developed for the analysis of strain-mediated interactions of vacancy lines in a pseudomorphic adsorbate system. The model was applied to Ga/Si(112) by extracting values for the microscopic parameters from total-energy calculations. This Frenkel-Kontorova model revealed that the mechanism of strain relaxation in the sub-monolayer adsorbate system was quite complex. In particular, the microscopic origins of attractive and repulsive interactions between vacancy lines were identified. That is, both of them were mediated by a combination of compressive and tensile bond strains within a single chain of Ga and Si atoms. The sum of these strain energies was minimized at a vacancy-line density which was very close to the experimentally observed value. The future analysis of similar strain-induced self-organized adsorbate systems was expected to benefit from this type of simple but accurate analytical model.

Frenkel-Kontorova Model of Vacancy-Line Interactions on Ga/Si(112) S.C.Erwin, A.A.Baski, L.J.Whitman, R.E.Rudd: Physical Review Letters, 1999, 83[9], 1818-21