  We present a model for the nuclear recoil ionization efficiency in silicon
based on an extension of Lindhard's theory where atomic bond disruption is
modeled as a function of the initial ion energy, the interatomic potential, and
the average ion-vacancy production energy. A better description of the
electronic stopping than the one assumed by Lindhard, the effect of electronic
straggling, as well as charge screening and Coulomb repulsion effects of ions
are also considered. The model describes the available data over nearly four
orders of magnitude in nuclear recoil energy.
