Linear scaling Coulomb and SCF exchange/correlation algorithms are not the end of the story as the ${\cal{O}}({N^{3}})$ diagonalization step has been rate limiting in semi-empirical techniques and, been predicted to become rate limiting in ab initio approaches in the medium term.Strout:1995 However, divide-and-conquer techniquesYang:1991a, Yang:1991b, Yang:1995, Lee:1996 and the recently developed quadratically convergent SCF algorithmOchsenfeld:1997 show great promise for reducing this problem.