Nonorthogonal tight-binding Hamiltonians for defects and interfaces in silicon

A computationally efficient and physically accurate method is desirable for simulation of solid-state phenomena that must be modeled by large atomic systems. To this end we present a nonorthogonal tight-binding model Hamiltonian based on the extended Huckel approach. Tests of existing parametrizations of this type of model Hamiltonian on geometries including some low-energy crystal structures, point defects, and surfaces reveal important shortcomings. We develop an improved parametrization and test it extensively on a wide range of crystalline defects and surfaces, and an amorphous sample. Our model is well suited to capture the energetics of crystalline, defective crystalline, and amorphous silicon.