Artificial opal-like structures based on spheres and colloidal particles have been fabricated in a
controlled way, presenting optical band-gap properties in the optical frequency range. Nonclose
packed artificial opals have also been fabricated and studied recently. In order to gain a better
understanding of these phenomena, we have studied macroscopic models of nonclose packed fcc
lattices using glass spheres (ε = 7) of 8 mm diameter, and measuring in the microwave region from
10 to 30 GHz. The results have shown a Bragg resonance tunable with filling factor of the opal, and
a strong rejected band similar, also present in close packed samples, much less affected by
compactness. The relation of this high order band with spheres single layer behavior is also
discussed
Performing a systematic review of our experimental data, we have realized that we introduced a significant mistake in our
abovementioned publication. Figure 3 did not correspond to the situation described, and should be changed by one here
included. The corrected data do not invalidate the conclusions presented in the original publication, even more they are
reinforced.
