For our analysis and discussion, it suffices to distinguish between critical points using so-called signatures, 𝜅, defined as the sum of the signs of the three eigenvalues of the Hessian. The critical points in molecules we will analyze are of two forms: 𝜅 = -3 indicates local maxima, such as positions of nuclei, where all curvatures are negative. A non-nuclear attractor (NNA) is a rare example of a CP located at off-nuclei positions. We will discuss one NNA in Li2. In contrast, 𝜅 = -1 corresponds to saddle points in the electron density, i.e., positions where the curvature in one direction is positive. The latter topological feature is commonly referred to as bond-critical points (BCPs) because they are often (but not always) found between neighboring atoms that are chemically bound. A BCP is a point of lowest electron density along a path of highest electron density; the lowest point along a ridge connecting maxima.