Variational volume integral equation method for electromagnetic scattering by irregular grains

An improved volume integral equation method for computing electromagnetic scattering by small particles is introduced. The features include: use of a variational technique (least squaring) instead of a collocation (point-matching) or Galerkin-method; analytical second order treatment of the singularity and its immediate surroundings; precise and effective quadratures. Comparisons to Lorenz-Mie theory, T-matrix method, DDA-code and experimental results are made. The new code is found to be significantly more accurate than other commonly used volume integral and DDA codes and does not require particle homogeneity and/or symmetry as some T-matrix codes do.