Theoretical insight into density and stability differences of RDX, HMX and CL-20

Cyclic nitramine explosives including RDX, HMX and CL-20 have drawn extensive attention due to their wide applications and excellent performance. However, these three nitramine explosives exhibit obviously different properties (such as density and thermostability) even though they share similar compositions and structures. Here, applying static calculations, we analyzed and disclosed the root of property differences from views of monomolecular parameters, intermolecular interactions and crystal packing. A high-precision method named binding energy in cluster (BEC) is proposed to analyze intermolecular interactions for molecules in a crystal. The polymorph and its effect on crystal density is discussed and the rationality of the BEC method is verified through comparing BECs in different polymorphs. This work may provide effective references for molecular design and structure-performance relationship analysis.