The energy of two-and three-dimensional materials. Our methodology for calculating the data shown in Figure is limited to molecules and one-dimensional polymers. For polymers with higher dimensional connectivity, we have relied on DFT calculations with periodic boundary conditions (see Methods). Figure shows our stability estimates for the 2D-and 3D polymers 10 and 11. Both systems are composed by tetrahedrally coordinated C and N atoms in a graphanelike configuration (Fig. ). Phonon band structures of 10 (including the isomers 10A and 10B) and 11, provided in the Supporting Information, confirm that these materials are dynamically stable. In other words, these structures all constitute local minima on the potential energy surface, which allows us to account for temperature effects in our relative stability estimates.