  Neutron scattering measurements have been performed on polycrystalline
samples of the newly discovered layered superconductor
LaO$_{0.5}$F$_{0.5}$BiS$_{2}$, and its nonsuperconducting parent compound
LaOBiS$_{2}$. The crystal structures and vibrational modes have been examined.
Upon F-doping, while the lattice contracts significantly along $c$ and expands
slightly along $a$, the buckling of the BiS$_2$ plane remains almost the same.
In the inelastic measurements, a large difference in the high energy phonon
modes was observed upon F substitution. Alternatively, the low energy modes
remain almost unchanged between non-superconducting and superconducting states
either by F-doping or by cooling through the transition temperature. Using
density functional perturbation theory we identify the phonon modes, and
estimate the phonon density of states. We compare these calculations to the
current measurements and other theoretical studies of this new superconducting
material.
