5 research outputs found
Acoustic properties of colloidal crystals
We present a systematic study of the frequency band structure of acoustic
waves in crystals consisting of nonoverlapping solid spheres in a fluid. We
consider colloidal crystals consisting of polystyrene spheres in water, and an
opal consisting of close-packed silica spheres in air. The opal exhibits an
omnidirectional frequency gap of considerable width; the colloidal crystals do
not. The physical origin of the bands are discussed for each case in some
detail. We present also results on the transmittance of finite slabs of the
above crystals.Comment: 7 pages, 9 figures, prb approve
Scattering of elastic waves by periodic arrays of spherical bodies
We develop a formalism for the calculation of the frequency band structure of
a phononic crystal consisting of non-overlapping elastic spheres, characterized
by Lam\'e coefficients which may be complex and frequency dependent, arranged
periodically in a host medium with different mass density and Lam\'e
coefficients. We view the crystal as a sequence of planes of spheres, parallel
to and having the two dimensional periodicity of a given crystallographic
plane, and obtain the complex band structure of the infinite crystal associated
with this plane. The method allows one to calculate, also, the transmission,
reflection, and absorption coefficients for an elastic wave (longitudinal or
transverse) incident, at any angle, on a slab of the crystal of finite
thickness. We demonstrate the efficiency of the method by applying it to a
specific example.Comment: 19 pages, 5 figures, Phys. Rev. B (in press