Theoretical Studies On The Structure And Absorption Spectra Of Cocrystal Explosives Under High Pressures

In the field of energetic materials,high-energy explosives have been widely used in military and civilian applications.The high-energy materials in current applications do not meet the requirements of high-energy and low-sensitivity at the same time.Therefore,seeking for new high-energy insensitive explosives has been becoming a hot topic in the field of the energetic materials.The eutectic technology of explosives can increase the stability of the explosive molecules and reduce their sensitivity.Thus,this has attracted great concern.In this thesis,periodic density functional theory with dispersion correction(DFT-D)method was used to study the structure and absorption spectra of three kinds of cocrystal explosives 3,5-diamino-1H-1,2,4-triazole(DAT)/5,5'-bis(trinitromethyl)-3,3'-azo-1H-1,2,4-triazole(BTNAT),benzofuroxime(BTF)/1,3,3-trinitroazetidine(TNAZ),N3,N6-di(1H-tetrazol-5-yl)-1,2,4,5-tetrazine-3,6-diamine(BTATz)/Pyrazine(PyA)under high pressures.The primary study contents of this thesis include the following points:1.It is found that the DAT/BTNAT cocrystal is anisotropic based on its calculations under hydrostatic compression of 0-100 GPa.It has two structural transformations occurred at 25 and90 GPa,respectively.The formation of new hydrogen bonding at 20 GPa is confirmed by the variation of the distances between N6 and H5 and betwen N1 and H6.As the pressure increases,the DAT/BTNAT cocrystal becomes more and more sensitive.To increase the pressure makes the DAT/BTNAT cocrystal possess high optical absorption activity.2.Based on the variation of the crystal structure of the BTF/TNAZ cocrystal under hydrostatic compression of 0-100 GPa,it is found that it has a structural transformation at 61 GPa.As the pressure increases,the band gap of the BTF/TNAZ cocrystal gradually decreases,and moreover,the gap reduction is more pronounced in the low-pressure range compared to the high-pressure region.In addition,the electronic delocalization of the BTF/TNAZ cocrystal obviously enhances.As the pressure increases,the optical absorption activity of the BTF/TNAZ cocrystal increases continually.3.The calculated results of the BTATZ/PyA cocrystal under hydrostatic compression of 0-200 GPa indicated that it has two structural transformations occurred at 80 and 110 GPa,respectively.The crystal volume of the BTATZ/PyA cocrystal gradually decreases with the increasing pressure,and moreover,the volume reduction is more pronounced in the lowpressure range compared to the high-pressure region.As the pressure increases,the DOS peaks in the top valence bands of the BTF/TNAZ cocrystal gradually shift to the higher energy,indicating that the electronic delocalization in the system increases.To increase the pressure makes the BTATZ/PyA cocrystal possess high optical absorption activity,and furthermore,its absorption region becomes wide.