Theoretical Investigations On The Structures And Stability For A Series Of Nitrogen-rich Molecules

Nitrogen-rich compounds as energetic molecules,have drawn considerable attention both theoretically and experimentally.But the high tension of structure and its intrinsic sensitivity to the environment,will reduce the stability of these molecules greatly.Therefore experimental synthesis of such compounds have certain difficulty and high risk.Using the computer aided molecular design method,explore high energy density compound with high stability can provide experimental synthesis HEDM candidate with outstanding performance.Detailed theoretical studies on the structures and stabilities of the nitrogen-rich based on the doping stratege are performed by using the quantum chemical methods.The main results are summarized as follows:?1?The structures and stability of nitrogen-rich compound X-CN₃?X=-NO₂,-NH₂,-H,-CN₃?were investigated in detail.The compound X-CN₃ can be viewed as a combination of energy building block and a theoretically stabled tetrahedral energetic structure unit.A series of higher-level energetic calculations had been carried out at the aug-cc-pVTZ//B3LYP/aug-cc-pVTZ,CCSD?t?/aug-cc-pVTZ//B3LYP/aug-cc-pVTZ,CBS-QB3,G4 levels.The kinetic stability of X-CN₃ were evaluated for the first time by studying the dissociation and isomerization barriers,as well as the Born-Oppenheimer molecular dynamic?BOMD?simulations.The present research discovers that creatively designed can potentially lead to promising candidates with high performance,moderately high thermal stability,and low impact sensitivity.?2?The singlet and triplet potential energy surface of nitrogen-rich compound PN₃ are initially constructed through global reaction route mapping method at the B3LYP/6-31G?d?level.The computations performed at the M06-2X/6-31+G?d,p?level identified 13 isomers and 21 transition states.The ground state isomer is the chain-like triplet PNNN?Cs?.The kinetic stability of PN₃ was evaluated by studying the dissociation,isomerization as well as the Born-Oppenheimer molecular dynamic?BOMD?simulations at the CCSD?t?/aug-cc-p VTZ//M06-2X/6-31+G?d,p?level.The results indicated that the chain-like triplet PNNN?Cs?and the tetrahedral-like singlet PN₃(C_3v)are both kinetically stable.Therefore,the two isomers,PNNN?C_s?and PN₃(C_3v)could act as promising building blocks for novel HEDMs.?3?Stable structures of positive nitrogen-rich compound BN₃^2-was studied.We used a global reaction route mapping?GRRM?method to search the singlet and triplet potential energy surface?PES?of BN₃^2-.The computations performed at the M06-2X/6-31+G?d,p?,CCSD?t?/aug-cc-p VTZ//M06-2X/6-31+G?d,p?,B3LYP/aug-cc-pVTZ,B3LYP/6-311+G?d?levels of the theory identified 8 isomers and 21 transition states.Based on CCSD?t?/aug-cc-p VTZ//M06-2X/6-31+G?d,p?method we explore reaction pathways by locating possible isomers,TSs,and dissociation channels on a PES.The kinetic stability of¹7was evaluated for the first time by studying the dissociation,isomerization and intersystem crossing barriers as well as the Born-Oppenheimer molecular dynamic?BOMD?simulations.We found that the ground state isomer¹7 kinetically stable.Finally,for more practical use,the isomers shows the potential to become building blocks for novel HEDMs.?4?The structures and stabilities of a series of CN₆ nitrogen-rich Molecules were investigated.To provide accurate spectroscopic properties,the CCSD?t?/aug-cc-pVTZ,G4,CBS-QB3 geometry optimization and frequency calculation were carried out.It is found that the unbranched structure is more stable than branched chain structure.The structure has a higher energy barrier when the carbon atom connecting the tetrahedral structure.The structure was unstable when the carbon atom sit at the bottom of four-sided pyramids.Through the analysis of thermodynamic and dynamic,we have obtained some structures?16?22?37?which can be used as candidates for high energy density materials.We have obtained some structures?1?3?4?14?15?which can be seen as metastable molecules.