A non-orthogonal tight-binding model Hamiltonian was developed which was based upon the extended Hückel approach. Tests of existing parametrizations of this type of model Hamiltonian, for geometries which included some low-energy crystal structures, point defects and surfaces, revealed important shortcomings. An improved parametrization was developed, and tested for a wide range of crystalline defects and surfaces, and for an amorphous sample. It was concluded that this model was well-suited to the treatment of the energetics of crystalline, defective crystalline, and amorphous Si.

N.Bernstein, E.Kaxiras: Physical Review B, 1997, 56[16], 10488-96