Conduction-band tight-binding description for Si applied to P donors

A tight-binding parametrization for silicon, optimized to correctly reproduce effective masses as well as the reciprocal space positions of the conduction-band minima, is presented. The reliability of the proposed parametrization is assessed by performing systematic comparisons between the descriptions of donor impurities in Si using this parametrization and previously reported ones. The spectral decomposition of the donor wavefunction demonstrates the importance of incorporating full band effects for a reliable representation, and that an incomplete real space description results from a truncated reciprocal space expansion as proposed within the effective mass theory.