  Heteroepitaxial strain can be a controlling factor in the lateral dimensions
of 1-D nanostructures. Bi nanolines on Si(001) have an atomic structure which
involves a large sub-surface reconstruction, resulting in a strong elastic
coupling to the surrounding silicon. We present variable-bias STM and first
principles electronic structure calculations of the Bi nanolines, which
investigates this interaction. We show that the strain associated with the
nanolines affects the atomic and electronic structure of at least two
neighbouring Si dimers, and identify the mechanism behind this. We also present
partial charge densities (projected by energy) for the nanoline with clean and
hydrogenated surroundings and contrast it to the clean Si(001) surface.
