Role of Surface-State Nesting in the Incommensurate Reconstruction of Mo(001)

First-principles total-energy calculations have been performed for the Mo(001) surface. Subsequent tight-binding calculations of the surface-phonon dispersion curves for the unreconstructed surface show that Fermi-surface nesting of surface states leads to a softening of surface modes near $\overline{M}$, with the maximum instability very close to the wave vector of the observed incommensurate reconstruction. Our results disagree strongly with the prevailing short-ranged force models for the incommensurate reconstruction on Mo(001).