Semi-empirical MO Investigation on Heats of Formation for Energetic Compounds

The fully optimized geometries of 66 energetic molecules have been calculated by means of four semiempirical MO methods (PM3?AM1?MNDO and MINDO/3). The heats of formation were obtained. The correlation between the calculated heats of formation of each method and experimental ones has been investigated. It is found that there is a good linear correlation between heats of formation calculated by PM3 method and experimental ones. The linear equation for these 35 compounds which have experimental values is ΔH_(f,EXP)=-4.98+1.03 ΔH_(f,cal) , the linear correlative coefficient,R, is 0.976, and the root mean square deviation is 37.53. The linear equation can be used to predict the gas-phase heats of formation of energetic compounds. The results calculated by AM1 method is not so good as the ones by PM3 method, while MINDO/3 and MNDO methods are not fit for calculating heats of formation of these compounds. Therefore, PM3 method is the best one for predicting heats of formation for energetic materials among the four semiempirical MO methods.