On the Use of AMl and PM3 Methods on Energetic Compounds

Stewart's new semi-empirical method MNDO-PM3 (PM3) is compared with the well known Dewar's AMl method in the study of nitrosubstituted compounds, and some energetic materials. PM3 method shows better performances than the AMl one. Adjacent lone pair/lone pair repulsion are better described at PM3 level and the known systematic correction of about ?9 kcal/mol for each C-NO₂ group of the AMl method becomes +3.5 kcal/mol at PM3 level. PM3 results for N-NO₂ containing compounds are directly comparable with experimental gas phase data.