Hi, May I ask you some questions on effective potential ? I've heard about Krammer potential ? Exactly, what is it ? Coulomb potential can be replaced by effective potential in some classical theory situation ? Now, my project is about the approximation of effective potential in short range and high temperature. I wonder if we have the fomula of effective potential and can we find the exact value of it with finite distance and temperature ? Can you help me ? My English is not good,but I hope you can get it.Thanks a lot.