  We present a highly efficient molecular dynamics scheme for calculating the
concentration profile of dopants implanted in group-IV alloy, and III-V zinc
blende structure materials. Our program incorporates methods for reducing
computational overhead, plus a rare event algorithm to give statistical
accuracy over several orders of magnitude change in the dopant concentration.
  The code uses a molecular dynamics (MD) model, instead of the binary
collision approximation (BCA) used in implant simulators such as TRIM and
Marlowe, to describe ion-target interactions. Atomic interactions are described
by a combination of `many-body' and screened Coulomb potentials. Inelastic
energy loss is accounted for using a Firsov model, and electronic stopping is
described by a Brandt-Kitagawa model which contains the single adjustable
parameter for the entire scheme. Thus, the program is easily extensible to new
ion-target combinations with the minimum of tuning, and is predictive over a
wide range of implant energies and angles.
  The scheme is especially suited for calculating profiles due to low energy,
large angle implants, and for situations where a predictive capability is
required with the minimum of experimental validation. We give examples of using
our code to calculate concentration profiles and 2D `point response' profiles
of dopants in crystalline silicon, silicon-germanium blends, and
gallium-arsenide. We can predict the experimental profile over five orders of
magnitude for <100> and <110> channeling and for non-channeling implants at
energies up to hundreds of keV.
