Theoretical Studies on Heats of Formation for Cubylnitrates Using Density Functional Theory B3LYP Method and Semiempirical MO Methods

摘要

The heats of formation(HOF )have been calculated for all the 21 cubylnitrate compounds using the semiemprical molecular orbital (MO) methods (MINDO/3, MNDO, AM1, and PM3) and for 8 of 21 cubylnitrates containg 1-4-ONO_2 groups using the density functional theory (DFT ) method at the B3LYP/6-31G level by means of designed isodesmic reactions . The cubane cage skeletons in cubylnitrate molecules have been kept in setting up isodesmic reactions to procuce more accurate and reliable results . It is forund that there are good linear relationships between te HOFs of the 8 cybylnitrates calculated using B3LYP/6-31G and two semiempirical MOI (PM3 and AM1) methods, and the linear correlation coefficients of PM3 and AM1 methods are 0.9901 and 0.9826 , respectively. Subsequently, the accurate HOFs at B3LYP/6-31G level of other 13 cubylnitrates containing 4-8 ONO_2 groups are obtained by systematically correcting their PM3- calculated HOFs. Compared with noncaged nitrates , all the 21 cubynitrates have highe heats of formation implying that they may be very powerful energtic materials and have highly explotable value. The relationship between the HOFs and the molecular structures of cubynitrates has been discussed