Theoretical study of solvent effects on RDX crystal quality and sensitivity using an implicit solvation model.

Density functional theory calculations using an SMD model were performed to investigate the effect of solvents (cyclohexanone, acetone, dimethyl formamide and dimethyl sulphoxide) on the crystal quality and sensitivity of RDX. The results indicate that the N-N bond length of the RDX molecule in solvents differs clearly from that in gas phase. The solvent effect on bond and dihedral angles of RDX molecule is small, however, the RDX molecule still maintains the AEE configuration. Natural population analysis shows that, due to solvation effects, RDX O atoms attract more electrons in solvents than in gas phase, while more positive charge distributes to the molecular skeleton. The calculations of N-NO2 bond BDE and nitro group charge as well as surface electrostatic potential parameters reveal that the solvent effect may be helpful to reduce the sensitivity of RDX, but this effect has an upper limit. Finally, it can be predicted qualitatively that the crystal quality of RDX crystallized from cyclohexanone and dimethyl sulphoxide will be higher than that from acetone and dimethyl formamide. Experimental results support these theoretical predictions.