Other models

It is possible to construct various other defect structures that act as double donors, involving different numbers of oxygen atoms (O_ni, $n \geq 3$). We have also modelled many of these for comparison with the di-y-lid model, and to determine whether they could be responsible for other members of the thermal donor family.

  

Figure 9.10: The top Kohn-Sham eigenvalues for various alternative thermal donor models, all in the +2 charge state. Black boxes denote filled state, white boxes for empty states. The eigenvalues have been arbitrarily scaled to the experimental band gap of 1.16eV. Structures are 3O_i species (a) Snyder/Stavola, (b) Partially dissociated trimer, 4O_i species (c) `Flanked square' model, (d) Di-square model, (e) 5O_i STD analogue, and (f) 6O_i di-y-lid with dimer in central Si-Si backbonds.