  We apply a stochastic version of an optimally tuned range-separated hybrid
functional to provide insight on the electronic properties of P- and B- doped
Si nanocrystals of experimentally relevant sizes. We show that we can use the
range-separation parameter for undoped systems to calculate accurate results
for dopant activation energies. We apply this strategy for tuning functionals
to study doped nanocrystals up to 2.5 nm in diameter at the hybrid functional
level. In this confinement regime, the P- and B- dopants have large activation
energies and have strongly localized states that lie deep within the energy
gaps. Structural relaxation plays a greater role for B-substituted dopants and
contributes to the increase in activation energy when the B dopant is near the
nanocrystal surface.
