A model, similar to an isodesmic reaction, is for the first time presented in this paper for describing, defining, and calculating the interaction energies of the indirectly linked groups or atoms within one molecule. Its applications to nitro substitutes of methane, benzene, and cubane verify its validity for a separate group of closely related compounds by the reasonable correlation between the calculated interaction energies of all substituted groups and the molecular stabilities or experimental impact sensitivities. Comparing with some existing rules of assessing the molecular stability, this so-called interaction energy is calculated using a model considering the chemical structures, that is, the electronic environments of compounds, and can be well related with the stabilities of nitro compounds. All investigation results show that the so-called interaction energy is a new, quantitative, and useful tool to evaluate the stabilities of nitro compounds