Calculation of the positron bound state with the copper atom

A relativistic method for the calculation of positron binding to atoms is presented. The method combines a configuration-interaction treatment of the valence electron and the positron, with a many-body perturbation-theory description of their interaction with the atomic core. We apply this method to positron binding by the copper atom and obtain a binding energy of 170 meV (±10%). To check the accuracy of the method we use a similar approach to calculate the negative copper ion. The calculated electron affinity is 1.218 eV, in good agreement with the experimental value of 1.236 eV. The problem of convergence of positron-atom bound-state calculations is investigated, and means to improve it are discussed. The relativistic character of the method and its satisfactory convergence make it a suitable tool for heavier atoms.