Abstract: A new transition-state calculation method based on the X.theory is presented,which includes the correlation effect with electronic self-interaction correction.Ionization potentials of atoms were calculated.The numerical results from the calculations indicate that correlation energy has a great influence on the ionization potential and the values of which are from-0.41 eVto 0.94 eV,The calculated results combmig the correlation effect are quite good.This new scheme has the advantage of simplicity and reasonableness,and can be applied to molecular calculation.

Key words: Correlation energy, Self-interation, Transition-state, lonization potential