Figure 3: Real space model of the PTCDA/Ag(110) brickwall layer.
From: Substrate-mediated band-dispersion of adsorbate molecular states

The iso-surfaces in purple show the partial charge density of the HOMO (left) and LUMO (right). Additionally horizontal cuts through the partial charge density visualize the delocalization of the LUMO within distinct planes specified in the two inset graphs (black indicates no, white high partial charge density). In the molecular plane (top panel) no delocalization occurs, contrary to the topmost Ag-plane (bottom panel) showing a significant delocalization.