Analysis of a Fast Fourier Transform Based Method for Modeling of   Heterogeneous Materials
  The focus of this paper is on the analysis of the Conjugate Gradient method applied to a non-symmetric system of linear equations, arising from a Fast Fourier Transform-based homogenization method due to (Moulinec and Suquet, 1994). Convergence of the method is proven by exploiting a certain projection operator reflecting physics of the underlying problem. These results are supported by a numerical example, demonstrating significant improvement of the Conjugate Gradient-based scheme over the original Moulinec-Suquet algorithm. 
J. Vond\v{r}ejc, J. Zeman and I. Marek
math.NA cond-mat.mtrl-sci physics.comp-ph