The application of local spin density approximation to a-Si and tetrahedral a-C

P.A. FEDDERS; D.A. DRABOLD; P. ORDEJÓN; G. FABRICIUS; D. SÁNCHEZ-PORTAL; E. ARTACHO; J.M. SOLER

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 1999 vol. 60 p. 10594 - 10597

1098-0121

We discuss the application of the local-spin-density approximation (LSDA) and provide criteria to gauge the reliability of supercell models of a−Si:H and tetrahedral amorphous carbon (ta−C). We identify models of a−Si:H that exhibit a localization on dangling bond consistent with electron-spin-resonance (ESR) experiments and show that a LSDA level description of the electron states is essential to describe these states. We offer an ab initio calculation of a well-isolated floating bond state and show that neither the charge nor spin is well localized. Finally, we suggest the origin of the ESR signal in ta−C is π-bonded pairs at the Fermi level.