Is everything correct? The formation enthalpy estimation and data revision of nitrate and perchlorate salts

Abstract

In modern searches for the structure of high-energy-density compounds with high operational,detonation, and physicochemical characteristics, a special place belongs to salts, which have anumber of significant advantages over neutral compounds. The development of this area ofHEDM is hampered by the lack of effective calculation schemes for estimating the enthalpy offormation DHf0 of salts, as a key parameter in assessing the prospects for their use. Based on theauthor's method (MICCM), which is superior in accuracy to currently available calculationmethods, the enthalpies of formation of various salts of nitrates and perchlorates for a promisingclass of high-energy amino-1,2,4-triazoles are calculated and the accuracy of calculations isestimated by other methods. Relationships between the thermochemical characteristics of saltsdepending on various cations are considered. Among the considered compounds, calculations ofthe enthalpies of salts of three amino-1,2,4-triazoles showed a significant discrepancy with theexperimental data. Calculations DHf0of salts were performed using three methods: volume-base thermodynamic(Jenkins/Bartlett method), the method of adding of ions contributions (MAIC, Matyushin'smethod), and the method of ions and cocrystals contribution mixing (MICCM, Khakimov'smethod). Calculations by the MICCM method were carried out on the basis of quantumchemistry methods (when estimating the enthalpies of formation in the gas phase) and themethod of atom-atom potentials (AAP) when calculating the enthalpy of sublimation of salts. Wehave optimized all the structures in the gas phase using the Becke three hybrid exchange andLee-Yang-Parr correlation functional with Grimme's dispersion correction, B3LYP-D2, and aug-cc-pVDZ basis set using the Gaussian16 software. The AAP calculations were performed usingthe FitMEP software packages (for adjusting the charges of the molecular electrostatic potential)and PMC (for the procedure for constructing crystal packings and searching for optimal ones).