Fast superposition T-matrix solution for clusters with arbitrarily-shaped constituent particles

•We present a fast superposition T-matrix for scattering by a cluster of particles.•Each particle in the cluster may be arbitrarily-shaped and inhomogeneous.•Constituent T-matrices are computed via the volume integral equation method.•The superposition T-matrix solution is accelerated by the fast multipole method.•Efficiency and accuracy of the method is demonstrated by numerical experiments.

A fast superposition T-matrix solution is formulated for electromagnetic scattering by a collection of arbitrarily-shaped inhomogeneous particles. The T-matrices for individual constituents are computed by expanding the Green's dyadic in the spherical vector wave functions and formulating a volume integral equation, where the equivalent electric current is the unknown and the spherical vector wave functions are treated as excitations. Furthermore, the volume integral equation and the superposition T-matrix are accelerated by the precorrected-FFT algorithm and the fast multipole algorithm, respectively. The approach allows for an efficient scattering analysis of the clusters and aggregates consisting of a large number of arbitrarily-shaped inhomogeneous particles.