An efficient family of optimal eight-order iterative methods for solving   nonlinear equations
  The prime objective of this paper is to design a new family of eighth-order iterative methods by accelerating the order of convergence and efficiency index of well existing seventh-order iterative method of \cite{Soleymani1} without using more function evaluations for finding simple roots of nonlinear equations. The presented iterative family requires three function and one derivative evaluations and thus agrees with the conjecture of Kung-Traub for the case $n = 4$ (i.e. optimal). We have also discussed the derivative free version of the proposed scheme. Numerical comparisons have been carried out to demonstrate the efficiency and the performances of proposed method. 
Anuradha Singh and J. P. Jaiswal
math.NA