plotting the Malavasi r**12 modified BKS potential

Dear all,
I am studying the anealing of silica recently, and I noticed the article Viod size distribution in MD-modelled silica glass structures by Malavasi 2005. A repulsive term D/r^12 was introduced to the BKS potential: E = Aexp(-r/rho) - C/r^6 + D/r^12 and the plot of the potential was attached. ( I think the title of the plotting in the article is wrong: the dash dot should represent the total potential and the solid line represent the Buckingham term.) I also plotted it. I noticed something differences existing, the picture attached.
My question is: Is the the differences between them normal? Will it affect my simulation?
Looking forward to your reponse. Thanks to your help.