The Formula of Entanglement Evaluation for Two-Electron Systems

The formula of entanglement evaluation for singleelectron systems is extended to that for two-electron systems.The accurate formula is derived for the concerrence between two arbitrary sites.It is pointed out that the effect of the interaction between particles on extanglement can be studied with the help of the evaluation of the site-averaged concurrence and spectrum-avaraged concurrence,and the localization properties of two-particle states can be studied with the help of entanglement.