content_image/365220.jpg content_image/365219.jpg
The corresponding contributions of the screened VP diagrams, depicted in Fig. 2(d)-(f), are 

<img src='content_image/365220.jpg'>

where U$_{VP}$ denotes the VP potential, and I$_{VP}$ (Δ) is the interelectronic-interaction operator modified by the electron-loop. For the renormalization of the expressions (23)-(26) we refer to the works [5, 65]. Accordingly, these contributions are divided into the Uehling and Wichmann-Kroll parts. The renormalized Uehling parts of the VP operators U$_{VP}$ and I$_{VP}$ (Δ) are given by the expressions (see, e.g., Ref. [5]) 

<img src='content_image/365219.jpg'>

where the density ρ$_{eff}$ is related to the nuclear binding and local screening potentials via the Poisson equation Δ V$_{nuc}$ ( r )+Δ V$_{scr}$ ( r ) = 4 παZρ$_{eff}$ ( r ). U scr VP differs from U$_{VP}$ only by replacing ρ$_{eff}$ with ρ$_{scr}$ , where the density ρ$_{scr}$ is related to the screening potential V$_{scr}$ . The Wichmann- Kroll parts of the expressions (23)-(25) are evaluated employing the approximate formula for the Wichmann-Kroll potential [66]. The Wichmann-Kroll contribution to Eq. (26) is relatively small [5] and is neglected in the present consideration. 

The numerical evaluation is based on the wave functions constructed from B-splines employing the dual-kinetic-balance finite basis set method [67]. The sphere model for the 

