Comparison between ab Initio and Modified INDO‐MO Calculations of N 20

Both STO‐3G ab initio and s‐p separation‐type‐modified INDO semiempirical methods were applied to molecular‐orbital calculation of the N 20 molecule. From these two methods, the optimized bond distances between the nearest N atoms (d n‐n ) and the most calculated thermodynamic data are close to each other. The positive values of ΔH a ° and ΔG a ° for the atomization reaction in this work prove that N 20 is stable. In contrast to conventional INDO and MINDO/3, but similar to former AMI and MNDO calculations, both ΔH r ° and ΔG r ° are positive in the formation reaction, which indicates that N 20 belongs to the category of high‐energy molecules.