DFT Studies On Structure And Properties Of Nitrogen Heterocyclic Energetic Ionic Salts

In the field of energetic materials for decades,it has been the main research direction for searching high-energy insensitive explosives with higher energy and better safety by balancing energy and safety.In this paper,some typical energetic ion salts(such as TKX-50,DNBTO,etc.)and energetic molecules(such as BCHMX)are used as the parent structures.Based on these parent structures,we designed a series of anions by modifying the functional groups.Then,by pairing these anions with some existed cations,a large number of energetic ion salts are formed.We used density functional theory(DFT)and volume-based thermodynamics(VBT)methods to systematically study the density,heats of formation,detonation performance and impact sensitivity of these series of energetic ion salts in order to effectively design potential energetic ion salts with better performance.The main contents of this paper are as follows:1.A series of energetic salts,which consist of simple amine cations(NH₄⁺,N₂H₅⁺and NH₂OH⁺)and pyrazole-based anions were designed.The anions were attached by substituents of-NH₂,-NO₂,-N₃,-NF₂ or-CN.The effects of different substituents and different ammonium cations on the properties of these salts were investigated.By comparing with the commonly used explosives RDX and HMX,we screened out the salts with high energy and acceptable sensitivity.2.Eleven novel bistetrazole diolated anions were designed by inserting different bridges into the dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate(TKX-50)framework.And lots of energetic salts were formulated from the bistetrazole diolated anions and ammonium-based cations.The effects of different bridges and different ammonium cations on the properties of these salts were investigated.According to our results,the construction of the nonnitro energetic anions like bistetrazole diolate and oxygenated cation like hydroxylammonium is a potential efficient way for screening out the high energy density materials with low sensitivity.3.We designed three novel cage energetic anions by introducing ionic bridges containing N^(?),N(O^(?))and N(N^(?)NO₂)into the cis-2,4,6,8-tetranitro-1H,5H-2,4,6,8-tetraazabicyclo[3.3.0]octane(bicyclo-HMX or BCMHX).Then,21 energetic ion salts were constructed by combining the caged anions with seven different cations.The effects of different ion bridges and different ammonium cations on the properties of these salts were investigated.By introducing ionic bridges into highly nitrated rings or modifying the original bridge with ionic bridges,some highly nitrated cage compounds with both excellent performance and low sensitivity could be developed strategically.4.Four series energetic anions were designed by introducing different deprotonation groups(–[N^(?)]–,–[N(O^(?))]–,–[N(N^(?)NO₂)]–,–[N(C^(?)(NO₂)₂)]–),substituent groups(–NO₂,–C(NO₂)₃)and N-bridging groups(–NH–,–NH–NH–,–N=N–,–N=N(O)–)into the bis-triazole framework.Then,based on these anions and ammonium-based cations(NH₄⁺,N₂H₅⁺and NH₂OH⁺),some energetic ion salts were formed.The effects of different groups and different ammonium cations on the properties of these salts were investigated.By converting energetic molecules with extremely excellent detonation properties into energetic ions,some highly nitrated energetic compounds with both excellent performance and low sensitivity could be developed strategically.