The Low Energy Electromagnetic package of the Geant4 toolkit incorporates a component for the simulation of atomic relaxation of elements with atomic number between 6 and 100. This process is triggered by the creation of a vacancy in the atomic shell occupancy as a result of an incident particle interaction with an atom of the target material. X-ray fluorescence and Auger electron emission result from the relaxation cascade. The availability of a model handling the atomic relaxation in Geant4 extends the applicability of the simulation toolkit to experimental use cases concerning the investigation of material properties through their characteristic X-ray or Auger emission. It is also relevant to precise simulation applications, like microdosimetry or the design and optimization of detectors based on nanotechnology. The key features of the software development process, the software architecture and design, and the implementation details of the physics model are described.