Application of the extended boundary condition method to homogeneous particles with point-group symmetries.

The numerical evaluation of surface integrals is the most time-consuming part of the extended boundary condition method (EBCM) for calculating the T matrix. An efficient implementation of the method is presented for homogeneous particles with discrete geometric symmetries and is applied to regular polyhedral prisms of finite length. For such prisms, an efficient quadrature scheme for computing the surface integrals is developed.

Application of the extended boundary condition method to particles with sharp edges: a comparison of two surface integration approaches.

We discuss, test, and compare two surface integration approaches that have been proposed for applying the extended boundary condition method (EBCM) to particles with sharp edges. One is based on approximating surface parameterization by a smooth function. By investigating the accuracy of this approach we find a quantitative condition for the radius of curvature of the approximate particle surface at the edge.

Can simple particle shapes be used to model scalar optical properties of an ensemble of wavelength-sized particles with complex shapes?

We compute the scalar optical properties of size-shape distributions of wavelength-sized randomly oriented homogeneous particles with different nonaxially symmetric geometries and investigate how well they can be modeled with a simple spherical, spheroidal, or cylindrical particle model. We find that a spherical particle model can be used to determine the extinction and scattering cross sections, the single-scattering albedo, and the asymmetry parameter with an error of less than 2%, whereas the extinction-to-backscatter ratio Reb is reproduced only with an error of 9%. The cylindrical and spheroidal particle models yield slightly improved results for Reb that deviate from those obtained for the complex particle ensemble by 7% and 5%, respectively.