The heat of formation (HOF) for a series of polynitroadamantanes was calculated systematically by using density functional theory (DFf) at B3LYP/6-31G* level by means of designed isodesmic reactions without breaking the adamantane skeleton (i.e. choosing adamantane as a reference compound). Empirical group addition method and semi- empirical MO (AMI, PM3, MNDO and MINDO/3) methods did not produce more accurate and reliable results for HOFs of the title compounds. The result from PM3 calculation is the best in tire four MO methods. The relationship between HOFs and molecular structures was discussed. It is found that the nitro group on the bridge C decreases HOF, whereas gem-dinitro groups increase HOF. The relative stability of the title compounds was illustrated according to the results calculated by HOFs, the energy gaps between the frontier orbitals and the bond order of C- NO_2. The obtained results provide basic data and regularity for the molecular design of new type of high energetic density materials.

Key words: polynitroadamantane, FORMATION HEAT, DFT, FRONTIER ORBITAL THEORY, STABILITY