z A CP is termed degenerate if the |det H| evaluated at this point yields a zero value. CT is a robust mathematical program that succeeded in describing all distinct changes in the geometric shape of (generic) parametric families triggered by the creation/annihilation of CPs through seven unfoldings constrained to have four parameters at most. One-state-variable unfoldings are called cuspoids, and their common characteristic is to have only one null eigenvalue. In contrast, parametric functions containing two state variables are referred to as umbilics, which describe changes in the geometric shape of a function resulting from two null eigenvalues. Eigenvalues result from a systematic sequence of algebraic operations applied to a square matrix, such as , H through a process called diagonalization. From a geometric standpoint, this procedure entails matrix rotations aimed at simplifying its form by eliminating mixed spatial-derivative terms. Possible combinations of critical points featuring a catastrophe can be straightforwardly found by combining the Poincaré-Hopf theorem and the maximum number of the unfolding CPs. Typical examples of fold in the ELF topography are the following: (attractor, saddle of index one) ↔ wp and (repellor, saddle of index 2) ↔ wp, where wp stands for a wandering point. For the cusp, one can have: (attractor, attractor, saddle of index one) ↔ attractor and (repellor, repellor, saddle of index 2) ↔ repellor. Recall that a wp is not a CP, and therefore it describes unbounded trajectories. For further on how to use the information provided in Table , let us reconsider the ammonia borane dissociation. We already showed that the fold characterizes the electron rearrangements of this reaction by following the |det H| at potentially degenerate CPs and their relative distance. This information is further verified using Poincaré-Hopf's relationship, yielding that one repellor and one saddle coalesced. Thus, this abrupt change should be described via a fold or an elliptic umbilic since these are the only functions with two CPs. However, the correct function is the fold since only one eigenvalue tends to zero value. Considering that the control parameter μ was conveniently defined as μ = d -d ͙ (where d and d ͙ correspond to the initial and bifurcation distances between reacting centers, respectively), the coalesce visualization and description is straightforward.