  The role of reduced dimensionality and of the surface on electron-phonon
(e-ph) coupling in silicon nanowires is determined from first principles.
Surface termination and chemistry is found to have a relatively small
influence, whereas reduced dimensionality fundamentally alters the behavior of
deformation potentials. As a consequence, electron coupling to "breathing
modes" emerges that cannot be described by conventional treatments of e-ph
coupling. The consequences for physical properties such as scattering lengths
and mobilities are significant: the mobilities for [110] grown wires are 6
times larger than those for [100] wires, an effect that cannot be predicted
without the form we find for Si nanowire deformation potentials.
