  We report on the phonon dynamics of LiYF4 obtained by direct method using
first principle calculations. The agreement between experimental and calculated
modes is satisfactory. An inversion between two Raman active modes is noticed
compared to inelastic neutron scattering and Raman measurements. The atomic
displacements corresponding to these modes are discussed. Multiple inversions
between Raman and infrared active groups are present above 360 cm-1. The total
and partial phonon density of state is also calculated and analyzed.
