The heats of formation (HOF) for all of the 21 polycyanocubanes are calculatedsystematicaly with density functional theory (DFT) B3LYP and semiempirical MO(MINO/3, MNDO, AM1 and PM3) methods. First, the accurate HOFs for the 9 titled compounds are obtained by means of designed isodesmic reactions at DFT-B3LYP/6-31G^* level, and the cubane cage skeletonhas not been broken (i.e. choosing cubane as a reference compound) to produced more accurate and reliable results. It is found that there are good linear relationships between the HOFs calculated using the B3LYP/6-31G^* and four semiempirical MO methods, respectively, and the linear correlation coefficient are all more than 0.999 4. The HOFs from AM1 calculation are the closest to the corresponding HOFs from B3LYP/6-31G^* results. Then, the accurate HOFs at B3LYP/6-31G^* level of other 12 polycyanocubanes are obtained by systematically correcting their AM1-calculated HOFs. Polycyanocubanes have very high HOFs, and the HOFs increase linearly with increasing in the number of cyano groups in a molecule. The results show that polycyanocubanes are the new generation explosives with high potentials and exploitable values.

Key words: CYANO GROUP, CUBANE, FORMATION HEAT, SEMIEMPIRICAL EQUATIONS, EXPLOSIVES