  Donors in silicon can now be positioned with an accuracy of about one lattice
constant, making it possible in principle to form donor arrays for quantum
computation or quantum simulation applications. However the multi-valley
character of the silicon conduction band combines with central cell corrections
to the donor state Hamiltonian to translate atomic scale imperfections in donor
placement into strongly disordered inter-donor hybridization. We present a
simple model that is able to account accurately for central-cell corrections,
and use it to assess the impact of donor-placement disorder on donor array
properties in both itinerant and localized limits.
