Predicting heats of formation of energetic materials using quantum mechanical calculations

Abstract

Quantum mechanical calculations are used to predict gas, liquid, and solid heats of formation of energetic molecules. A simple atom-equivalent method converts quantum mechanical energies of molecules and their atomic constituents to gas-phase heats of formation of energetic materials. Functional relationships between heats of vaporization and sublimation and properties associated with quantum mechanically determined electrostatic potentials of isolated molecules are established. These are used with the gas-phase heats of formation to predict condensed-phase heats of formation. The calculated gas-phase heats of formation have a root mean square (rms) deviation of 3.1 kcal/mol and a maximum deviation of 7.3 kcal/mol from 35 experimental values. The rms and maximum deviations of predicted heats of vaporization from 27 experimental values are 1.7 and 6.1 kcal/mol, respectively. The rms and maximum deviations of predicted heats of sublimation from 36 experimental values are 3.6 and 12.4 kcal/mol, respectively. The rms and maximum deviations of predictions of liquid heats of formation from 41 measured values (corresponding to 24 molecules) are 3.3 and 9.3 kcal/mol, respectively. Similarly, the rms and maximum deviations of predictions of solid heats of formation from 75 measured values (corresponding to 44 molecules) are 9.0 and 35.4 kcal/mol, respectively.