First-principles calculations were made of the structural and dynamic properties of (001) surfaces. The computations were performed using density-functional theory and density functional perturbation theory. The calculated reconstruction parameters showed excellent agreement with previous theoretical investigations and experimental data. The phonon dispersion in the tilted dimer p(2 x 1) reconstruction was first determined. The surface vibrations of Si(001) deviated from those of Ge(001) by characteristic shifts in the frequency of the phonon modes. This was related to chemical trends in the reconstruction behavior. Complete dispersion curves of the surface modes of the c(4 x 2) and p(2 x 2) phases were determined by using local-coupling transfer, which was a method for modelling the dynamic matrices of large-sized superstructures. The phonon modes of the higher-order reconstructions exhibited trends which were similar to those of the p(2 x 1) reconstructions. The interpretation of experimental data on inelastic He-atom scattering indicated a correlation of the surface dimers with local c(4 x 2) or p(2 x 2) symmetry at room temperature.

Structural and dynamic properties of Ge(001) in comparison with Si(001) and C(001) W.Stigler, P.Pavone, J.Fritsch: Physical Review B, 1998, 58[20], 13686-97