1,1-Diamino-2,2-dinitroethylene recently synthesized is a new energetic compound, which may be an insensitive high explosive (IHE). In this paper, the fully optimized molecular geometries and the total energies of diamino-dinitroethylene compomnds, 1,1-diamino-2,2- dinitroethylene(Ⅰ), cis(Ⅱ) and trans (Ⅲ) 1,2-diamino-1,2- dinitroethylene, have been calculated using ab initio method at the HF/6-31G^*^*, MP2/6-31G^*^*//HF/6-31G^*^* level and DFT method at B3LYP/6-31G^*^* level, respectively. The result shows that the order of stability of the title compounds is Ⅰ>Ⅲ>Ⅱ, thermodynamically. There exist strong intramolecular hydrogen bonds between nitro oxygen atoms and amino hydrogen atoms of the titled compounds and the hydrogen bond intensities of the title compounds are Ⅰ>Ⅲ>Ⅱ. Their frontier orbital energy gaps (△E) are Ⅰ>Ⅱ>Ⅲ. Based on the analysis of molecular geometry and frontier orbital component, it is found that the π-electron conjunction and delocalization of the title compounds are Ⅰ≈Ⅲ>Ⅱ. The computed vibrational frequencies of 1,1-diamino-2,2-dinitroethylene is in good agreement with the corresponding experiment results. The thermodynamic properties of DADNE were also calculated and discussed. These data are helpful to the molecular design of new IHE.

Key words: AB INITIO CALCULATION, STABILITY, INFRARED SPECTROPHOTOMETRY, THERMODYNAMIC PROPERTIES