  We present a tight binding theory of the Dirac point resonances due to
adsorbed atoms and molecules on an infinite 2D graphene sheet based on the
standard tight binding model of the graphene p-band electronic structure and
the extended Huckel model of the adsorbate and nearby graphene carbon atoms.
The relaxed atomic geometries of the adsorbates and graphene are calculated
using density functional theory. Our model includes the effects of the local
rehybridization of the graphene from the sp^2 to sp^3 electronic structure that
occurs when adsorbed atoms or molecules bond covalently to the graphene. Unlike
in previous tight-binding models of Dirac point resonances, adsorbed species
with multiple extended molecular orbitals and bonding to more than one graphene
carbon atom are treated. More accurate and more general analytic expressions
for the Green's function matrix elements that enter the T-matrix theory of
Dirac point resonances than have been available previously are obtained. We
study H, F, OH and O adsorbates on graphene and for each we find a strong
scattering resonance (two resonances for O) near the Dirac point of graphene,
by far the strongest and closest to the Dirac point being the resonance for H.
We extract a minimal set of tight binding parameters that can be used to model
resonant electron scattering and electron transport in graphene and graphene
nanostructures with adsorbed H, F, OH and O accurately and efficiently. We also
compare our results for the properties of Dirac point resonances due to
adsorbates on graphene with those obtained by others using density functional
theory-based electronic structure calculations, and discuss their relative
merits. We then present calculations of electronic quantum transport in
graphene nanoribbons with these adsorbed species...
