Total-energy pseudopotential calculations were used to investigate a number of surface reconstructions on germanium. The system of buckled dimers on the (001) surface of germanium could be represented by a spin system. The interactions between the dimers were represented by interactions between the spins. The values of the interaction parameters in an effective Hamiltonian that describes the system of dimers were determined by calculating the energies of the (2 x 1), c(4 x 2), p(2 x 2) and p(4 x 1) arrangements of buckled dimers. The Hamiltonian gives a prediction of 280 to 480K for the temperature of the order-disorder phase transition on the surface. The mechanism responsible for stabilising the Takayanagi reconstruction of the (111) surface of germanium was investigated by calculating the energies of the (3 x 3) Takayanagi structure and of sub-elements of this structure. It was shown that the Takayanagi reconstruction was stabilised by an interaction between the adatoms and the dimers in the second layer of atoms. The surface stresses of the complete Takayanagi structure and of the Takayanagi structure without adatoms were calculated and it was found that the surface energy was not related to the magnitude of the surface stress. preliminary results for the c(2 x 8) reconstruction of the (111) surface of germanium were presented.

Surface Reconstructions on Germanium. M.C.Payne, M.Needels, J.D.Joannopoulos: Journal of Physics - Condensed Matter, 1989, 1[SB], 63-74