The discrete dipole approximation

The discrete dipole approximation permits the calculation of the scattering and absorption cross-section of particles or arbitrary geometery. The first step in DDA modelling is to break the target geometry into a cubic array of dipoles.

family of rods

In the case of the nanorods shown above (typically 10nm in diameter and with aspect ratios up to 6 or 8), we are particularly interested in the relationship between the spectrum generated by the rod and the spectra of the inscribed and exscribed cylinders.

rod in relation to cylinder

Results from simulations of the extinction cross-section for these rods and cylinders can now be compared with some sample experimental data [1].

DDA and experimentally determined extinction

We are also interested in the spectra generated by geometries including triangular and hexagonal prisms.

Other shapes: triangular prism


  1. Gold nanorod extinction spectra. SW Prescott and P Mulvaney. Journal of Applied Physics, 99, 123504, 2006.

Last edited: Tuesday September 9, 2008

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