The limitations to our selection are motivated by practicality. The full structural space of possible HCN-derived polymers and molecules is immense. For example, one automated search for reactions that result in HCN tetramers identified 678 compounds. Several other structures have also been computationally predicted. We consider here consider a selection of pure HCN-based materials, i.e., structures where the stoichiometry of H, C and N are 1:1:1 (and no additional elements). Other HCN-based materials can incorporate oxygen, additional nitrogen and hydrogen or form through condensation reactions, e.g., through the formation of NH3. Such materials, which may also be important, are beyond the scope of this work. In what follows, we will first introduce the materials we study, and then proceed to evaluate their relative thermodynamic stability.