  Short dangling bond wires (DB wires), fabricated on H-terminated Si(001)
surfaces, show patterns of displacement that depend on their length. We have
performed density function calculations, with and without spin-polarisation,
designed to investigate the atomic and electronic structure of these wires. As
expected, we find that even length wires are accurately modelled by non-spin
polarised calculations, whilst odd length wires must be modelled using
spin-polarised calculations. In particular, the use of spin-polarisation
provides quantative agreement with STM observations, rather than the
qualitative agreement reported elsewhere.
