The phonon dispersion of the Ge(001) surface has been calculated using density-functional perturbation theory and local-coupling transfer, which is a novel method for modeling dynamical matrices of large-size superstructures, such as the $c$( $4\times 2$) and $p$( $2\times 2$) phases. Furthermore, the surface phonons have been determined by inelastic He atom scattering. The measured scattering intensities can be explained only if higher-order reconstructions are assumed, indicating a correlation of the surface dimers with local $c$( $4\times 2$) or $p$( $2\times 2$) symmetry in Ge(001) at room temperature.

• Received 11 March 1997

DOI:https://doi.org/10.1103/PhysRevLett.79.1090