Effects Of Amino Groups On The Structures And The Properties Of Explosives

It is one of the most important topics of explosives to design and synthesize newpure low sensitive high ones (IHE). The sensitivities and energy densities of explosivesare governed by their multiscale structures, among which the explosive molecules arethe bases of these structures and one of the factors determining their structures and theproperties in principle. The molecular structure and the condensed structures, and theirsensitivities and energy densities of an explosive can be changed obviously afterintroduction of one or more amino groups.The sensitivities and energy densities of amino derivatives of acyclic hydrocarbons,aliphatic heterocycle, cage and aromatic ring were predicted using GGA/PBE,LDA/PWC, PM3calculations and K-J equation. The sensitivity is assessed by bonddissociation energy (BDE), the bond length (R), and the nitro group charges(Qnitro). Thedetonation properties including detonation velocities (D) and pressures (P) arecalculated by using Kamlet–Jacbos equation. As a result, the calculated densities areclosed to the experimental densities, suggesting the method is reliable. Moreoner, aminogroups in a conjugated system and ortho-or para-relative to nitro groups are helpful toenhance the molecular stability and energy density; while those in a non-conjugatedsystem lead to the reduction of molecular stability with no improvement of energydensities.The mechanism of TATB molecules stacking to a quasi-regular or regularhexagonal TATB crystal was discussed using a combined method of a density functionaltheory BLYP and Dreiding forcefield. As a result, we found that there are two styles toform the most energetically favored TATB dimers: a hydrogen bonding along themolecular plane and an offset π-stacking vertical to the plane, just leading to theoutspread and the thickening of the regular hexagon during the crystal growth,respectively. At the same time, the TATB molecules or layers are arranged on the crystalface always along the special orientation of a regular hexagon and other orientations arestrongly thermodynamically forbidden, resulting in a hexagonal crystal bulk. Thesimulations agree well with the experiment.Some properties of a complex of the TATB/graphene layers overlaid alternately arepredicted by COMPASS forcefiled and LDA-PWC method, and the results as follow:interlayer distance,3.4; enthalpy of formation,-121.8kJ/mol; packing density,2.112 g/cm3; increased band gap relative to graphite,0.2eV, detonation enthalpy,1.61kJ/g;detonation pressure,10.5GPa; detonation velocity,2.40km/s; and lubricating propertyis better than graphite. By adjusting the number proportion and the overlaying order ofthe two kinds of layers, a series of complexes with adjustable properties can beobtained.All these results indicate that amino groups in explosives can influence theirstructures and properties notably.