  The behaviors of barrier characteristics and fusion cross sections are
analyzed by changing neutron over wide range of colliding systems. For this
purpose, we have extended our previous study (Eur. Phys. J. A \textbf{48}, 21
(2012), it is devoted to the colliding systems with neutron-rich nuclei) to 125
isotopic systems with condition of $0.5\leq N/Z \leq 1.6$ for their compound
nuclei. The AW 95, Bass 80, Denisov DP and Prox. 2010 potentials are used to
calculate the nuclear part of interacting potential. The obtained results show
that the trend of barrier heights $V_B$ and positions $R_B$ as well as nuclear
$V_N$ and Coulomb $V_C$ potentials (at $R=R_B$) as a function of ($N/Z-1$)
quantity are non-linear (second-order) whereas the fusion cross sections follow
a linear-dependence.
