M. S. Kushwaha P. Halevi
Inst. de Fisica, Univ. Autonoma de Puebla, Apdo. Post. J-45, Puebla 72750, Mexico
The first extensive band structure calculations in periodic structures made up of liquids and gases are reported. The specific system studied in the present investigation is spherical air (water) balloons in a periodic pattern in water (air)---the fcc arrangement. Since only longitudinal waves can propagate, the general wave equation is greatly simplified. The pertinent parameters are the densities and the longitudinal-sound velocities. Depending upon the filling fraction a number of band gap(s) extending over the whole first Brillouin zone are found. Within these band gaps vibrations and sound propagation are prohibited. A complete acoustic gap or zero density of states should have important consequences for the realization of noiseless environment and for the localization of longitudinal sound waves. The precise dependence of the band gaps on the filling fraction is also investigated.