The application of NCI analysis is not limited to isolated systems; it can also be used to study noncovalent interactions in periodic systems. For example, Fig. shows the NCI map of a typical covalent organic framework compound, generated by the Multiwfn code based on the wavefunction obtained from periodic DFT calculations using the CP2K program. The map fully illustrates the infinitely extended - interactions between the two layers, intralayer hydrogen bonds (blue areas), steric hindrance (dark brown and red areas), vdW interactions (green areas), and more. There are numerous other examples of the application of the NCI method in the literature. For instance, Ref. used the NCI method to intuitively illustrate the adsorption of different small molecules by the novel cyclo [18]carbon molecule. In