The effects of shapes and symmetries of scatterers on the phononic band gap in 2D phononic crystals

The phononic band structures of two-dimensional solid phononic crystals consisting of lattices with different symmetry and scatterers of various shapes, orientations, and sizes are studied numerically. Specifically, three types of lattices (triangular, hexagonal and square) and four different shapes of scatterers (hexagon, circle, square and triangle) are considered. Given a lattice symmetry, the largest absolute phononic band gap is achieved when the scatterer has the same shape and orientation as that of coordination polygon of a lattice point; e.g., hexagonal rods in triangular lattices, triangular rods in honeycomb lattices and square rods in square lattices. The band gap can be varied by adjusting the orientation and size of the scatterers; if the maximum allowed filling fraction of scatterers increases after rotation, the normalized gap width will enlarge, otherwise the normalized gap width will decrease. (C) 2004 Elsevier B.V. All rights reserved.