Fig. 7: Crystal structure and electrostatic potential maps for different cuts along c in units of the lattice parameter.
From: Absence of magnetic order in RuO2: insights from μSR spectroscopy and neutron diffraction

The electrostatic potential is represented by the color map from red to blue. The purple shade indicates regions where the (negative) electrostatic potential is the largest, i.e., the likely muon stopping sites. The color map is limited to the unit cell.