A structural model of hydrogenated amorphous Si containing an isolated dangling bond was used to investigate the effects of electron interactions on the electronic level splittings, localization of charge and spin, and fluctuations in charge and spin. These properties were calculated with a recently developed density-matrix correlation-energy functional applied to a generalized Anderson Hamiltonian, consisting of tight-binding one-electron terms parametrizing hydrogenated amorphous Si plus a local interaction term. The energy level splittings approach an asymptotic value for large values of the electron-interaction parameter U, and for physically relevant values of U were in the range of 0.3 to 0.5eV. The electron spin was highly localized on the central orbital of the dangling bond while the charge was spread over a larger region surrounding the dangling bond site. These results were consistent with known experimental data and previous density-functional calculations. The spin fluctuations were quite different from those obtained with unrestricted Hartree-Fock theory.

Electronic Structure of Dangling Bonds in Amorphous Silicon Studied via a Density-Matrix Functional Method. R.G.Hennig, P.A.Fedders, A.E.Carlsson: Physical Review B, 2002, 66[19], 195213 (6pp)