M. S. Kushwaha P. Halevi
Inst. de Fisica, Univ. Autonoma de Puebla, Apdo. Post. J-45, Puebla 72570, Mexico
The acoustic band structure of periodic elastic composites were calculated using position-dependent density and elastic constant. The specific system investigated is made up of a periodic array of parallel metallic rods of circular cross section whose intersections with a perpendicular plane from a hexagonal lattice. The rods are embedded in a background medium with different elastic constant and density. The transverse polarization was considered---with displacement u(r,t) parallel to the cylinders (and perpendicular to the Bloch wave vectors). The absolute band gaps extending throughout the first Brillouin zone were found in the low-frequency regime. The specific case studied was Cu(Al) cylinders in the Al(Cu) background. A direct comparison of the hexagonal case with the square-lattice pattern (Kushwaha et al., preceding abstract in this session) reveals that the widths of these band gaps are larger in the case of hexagonal lattices. The precise dependence of the gaps on the filling fraction is investigated.