The fundamental assumption underlying the CoGEF approach is that an external force will lead to a distortion of the molecular structure relative to its equilibrium geometry. Consequently, if we impose the deformation by application of geometrical constraints, one can calculate the force leading to this deformation via the energy change necessary to generate this new geometry. In the 1D-CoGEF approach, a relaxed potential energy scan is performed, incrementally increasing the distance between two atoms to simulate pulling apart of those atoms by an external force. The simplest example of such an approach is a well-known relaxed potential energy scan (PES) of a bond coordinate (Figure ). In this example, the bond distance between the two blue carbon atoms is gradually increased and kept constrained, while all other coordinates of the molecule are fully relaxed. This results in a minimum energy profile of the covalent bond as a function of the interatomic distance. We term this energy profile a bond potential energy surface (BPES).