Theoretically new high-energy and -density materials (HEDM) in which the hydrogens on RDX and β-HMX (hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, respectively) were sequentially replaced by (N-NO2)x functional groups were designed and evaluated using density functional theory (DFT) calculations in combination with the Kamlet-Jacobs equations and an atoms-in-molecules (AIM) analysis. Improved detonation properties and reduced sensitivity compared to RDX and β-HMX were predicted. Interestingly, the RDX and β-HMX derivatives having one attached N-NO2 group [RDX-(NNO2)1 and HMX-(NNO2)1] showed excellent detonation properties (detonation velocities: 9.529 and 9.575 km∙s−1, and detonation pressures: 40.818 and 41.570 GPa, respectively), which were superior to the parent compounds. Sensitivity estimations obtained by calculating impact sensitivities and HOMO-LUMO gaps indicated that RDX-(NNO2)1 and HMX-(NNO2)1 were less stable than RDX and HMX but more stable than any of the other derivatives. This method of sequential NNO2 group attachment on conventional HEDMs offers a firm basis for further studies on the design of new explosives. Furthermore, the newly found structures may be promising candidates for better HEDMs.