  The stretching and bending vibrational spectrum and the intensities of
infrared transitions in a tetrahedral molecule are studied in two
boson-realization models, where the interactions between stretching and bending
vibrations are described by a quadratic cross term and by Fermi resonance
terms, called harmonically coupled and Fermi resonance boson-realization model,
respectively. The later is a development of our recent model. As an example,
the two models are applied to the overtone spectrum and the intensities of
silicon tetrafluorde. Those models provide fits to the published experimental
vibrational eigenvalues with standard deviations 1.956 cm$^{-1}$ and 0.908
cm$^{-1}$, respectively. The intensities of infrared transitions of its
complete vibrations are calculated in the two models, and results show a good
agreement with the observed data.
