Prediction Model for Coformer Screening of Energetic Eutectics Based on Flory-Huggins Interaction Parameter

Based on intermolecular interactions, Flory-Huggins interaction parameter chi(AB)>0 was presented as a prediction model to screen the coformer of energetic eutectics. To evaluate the predictive accuracy of this model, 80 energetic eutectics were collected from literatures. The molecular structures were optimized by computationally cheap molecular mechanics and high precision dispersion-corrected density functional, respectively. Then the weighted Monte Carlo method was used to calculate the mixing energy Delta E-mix of the binary system and thus derive the dimensionless chi(AB). The results show that the prediction accuracy is up to 85% based on M06-2X-D3/6-311+G (d, p) optimization geometry and RESP charge, much greater than 45% of molecular mechanics method. Furthermore, size/shape mismatch between eutectic molecules was considered by shape index and molecular volume to enrich the prediction model. Based on this prediction model, a new energetic eutectic MTNP-TNT was discovered, whose chi(AB) value is 3.376 obtained by M06-2X-D3/6-311+G (d, p) method. Experimentally, the classical "V" phase diagram drawn from the differential scanning calorimetry (DSC) data also suggests the MTNP-TNT eutectic with eutectic temperature of 54.41 degrees C at the molar ratio of 51.50: 48.50. Theoretical and experimental results successfully validate the chi(AB)>0 prediction model for screening the coformers of energetic eutectics. This work opens a way for the crystal engineering of energetic eutectic solid forms with attractive physicochemical properties using a computational approach.