ENERGIES AND STRUCTURAL-PROPERTIES OF HYDROGEN AND RELATED DEFECTS IN MOLECULAR-DYNAMICS-MODELED A-SI-H

We use ab initio pseudopotential local-density-approximation methods to create and study related supercells containing 62 Si atoms and from five to seven H atoms. In particular, we obtain energies and structural properties of ii in different charge states that are passivating dangling bonds, in bond-centered positions, and in other interstitial sites. The most striking;result found is the rather large (of order 1 eV) spread of energies for a given type of defect, depending on its surroundings. We also find that changes in single particle energies or energy eigenvalues from defect to defect are not particular close to changes in the total energy and that the distinction, between. bond-centered H and a dangling bond plus a Si-H bond, is not as clear cut as one might think. The calculations also provide insights into possible migration mechanisms and energies for H movement.