Theoretical studies on heats of formation for polynitrocubanes using the density functional theory B3LYP method and semiempirical MO methods

Abstract

AbstractThe heats of formation (HOFs) have been calculated for 21 polynitrocubane compounds using semiempirical MO methods (MINDO/3, MNDO, AM1 and PM3) and for eight of 21 polynitrocubanes containing one to four nitro groups using the density functional theory method at the B3LYP/6‐31G* level by means of designed isodesmic reactions. The cubane cage skeletons in the polynitrocubane molecules have been kept in setting up the isodesmic reactions to produce more accurate and reliable results. It is found that there is a good linear relationship between the HOFs of eight polynitrocubanes calculated using the B3LYP/6‐31G* and PM3 methods, but not for the other methods, and the linear correlation coefficient equals 0.9971. Subsequently, accurate HOFs at the B3LYP/6‐31G* level of the other 13 polynitrocubanes containing four to eight nitro groups were obtained by systematically correcting their PM3‐calculated HOFs. All 21 polynitrocubane compounds have high HOFs, implying that they can be very powerful energetic materials. The relationship between the HOFs and molecular structures for polynitrocubanes is discussed. Copyright © 2001 John Wiley & Sons, Ltd.