An easy pathway for reliable assessment of crystal density of high nitrogen-containing salts and ionic liquids without using complex descriptors

Abstract

High nitrogen-containing salts and ionic liquids (HNCSILs) have more than 50% W/W nitrogen in their chemical formula. They offer many advantages over traditional molecular energetic compounds, e.g. lower vapor pressures, higher densities, and enhanced thermal stability in many cases as compared to their atomically similar non-ionic analogs. The largest available experimental data including 310 CHNO compounds have been collected from various sources, where they were used for deriving and testing the new model. The new model requires only elemental composition and specific groups of cations and anions for reliable prediction of crystal density of different types of HNCSILs. The high reliability of the new method is compared with the calculated results of one of the best available quantitative structure-property relationship (QSPR) methods. The values of Root Mean Square Error (RMSE) of the training set containing 266 HNCSILs are 0.054 and 0.102 g/cm3 for the new and comparative models, respectively. The value of RMSE of the new model for the test set containing 44 HNCSILs is also 0.0472 g/cm3, which is considerably less than the comparative model, i.e. 0.0951 g/cm3. For further 31 HNCSILs as an external test set, where computational results for one of the best complex model of molecular surface electrostatic potential (MSPE) were available, the RMSE values for the new and comparative MESP-based methods are 0.060 and 0.065 g/cm3, respectively.