Ab initio Study of Electronic Structure and Properties in Crystalline 1,1,3,3,5,5‐Hexaazidocyclotriphosphazene

Abstract

The banding and electronic structures of crystalline 1,1,3,3,5,5-hexaazidocyclotriphosphazene (P 3 N 21 ) have been investigated at DFT-B3LYP/6-31G(d) level. Relaxed crystal structure compares well with experimental data. The energy gap is 5.57 eV, indicating that P 3 N 21 is an insulator. The frontier orbital is mainly formed by atomic orbitals of azido group, so it is the most reactive part of the molecule. The intermolecular interaction is strong along the direction that is nearly perpendicular to the phosphazene ring. The distribution of electrostatic potential is quite uneven, so P 3 N 21 has a very high impact sensitivity. The point charge electrostatic potential is very high between the azido groups of the neighboring molecules, which indicates that the crystal lattice in this position may easily be broken and becomes the explosion center when P 3 N 21 is impacted. The overlap populations of P-N α bonds are much less than those of other bonds, therefore the P-N α bonds first rupture by external stimuli, which agrees well with the experimental study of mass spectrum.

Theoretical Study for High-Energy-Density Compounds Derived from Cyclophosphazene. IV. DFT Studies on 1,1-Diamino-3,3,5,5,7,7-hexaazidocyclotetraphosphazene and Its Isomers

“…In previous publications, we have ever reported the preparation, structural characterization, and theoretical studies of 1,1-spiro(ethylenediamino)-3,3,5,5-tetrachlorocyclotriphosphazene and its nitration product [ 10 ]. In addition, the high nitrogen-contented energetic compounds 1,1,3,3,5,5,7,7-octaazidocyclotetraphosphazene [ 11 ] and 1,1,3,3,5,5-hexaazidocyclotriphosphazene [ 12 ] have been investigated using the quantum chemistry method. As a part of a series of research works on high-energy-density compounds derived from cyclophosphazene, we have performed theoretical studies on the five isomers diaminohexaazidocyclotetraphosphazene ( i.e., 1,1-diamino-3,3,5,5,7,7-hexa-azido-cyclotetraphosphazene ( I ), trans -1,5-diamino-1,3,3,5,7,7-hexaazidocyclotetraphosphazene ( II ), cis -1,5-diamino-1,3,3,5,7,7-hexaazidocyclotetraphosphazene ( III ), trans -1,3-diamino-1,3,5,5,7,7-hexa-azidocyclotetraphosphazene ( IV ) and cis -1,3-diamino-1,3,5,5,7,7-hexaazidocyclotetraphosphazene ( V ), Figure 1 ).…”