title: Calculation of Atomic Elastic Scattering Cross Sections of Electrons and Positrons authors: Jiri Stepanek, Osvaldo Moreira affiliations: Paul Scherrer Institut (PSI), CH-5232 Villigen PSI, Switzerland summary: Variationally optimized effective atomic potential is calc- ulated solving relativistic Dirac equations, whereas direct (or Hartree) part of the potential is obtained in a straight- forward way from the electron density. The "variationally optimum" exchange potential for bound electrons is calculated