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Micro-defects in an energetic material is an important factor for the formation of “hot spots” and successive explosive detonation. However, an understanding of the micro-mechanism of forming “hot spots” is limited and the development and application of energetic materials are hindered due to the less knowledge of micro-defects inside the materials. In order to understand the characteristics of micro-defects and explore the basic mechanism of forming “hot spots” caused by defects, the effects of molecular vacancy defect on the geometrical structure, electronic structure and vibration characteristics of Hexogeon (RDX) energetic materials are studied using the first-principle method, and the basic formation mechanism of initial “hot spot” is discussed. The effects of molecular vacancy defect on the RDX geometrical structure, electronic band structure, electronic density of states and frontier molecular orbitals are analyzed using the periodic model, while the influences of molecular vacancy defect on the vibration characteristics of RDX systems are calculated using the cluster model. Infrared vibration spectra and vibration characteristics of the internal molecules at the same vibration frequency for the perfect and defective RDX systems are obtained. It is found that vacancy defect makes the N–N bond near the defect long, and the molecular structure loose; some degenerate energy levels in the conduction band present separation and the electronic density of states decreases; the bottom of the conduction band and the top of the valence band contributed by N-2p and O-2p orbitals shift to the Fermi surface, which reduces the energy band gap and increases the activity of system. At the same time, the calculations of the frontier molecular orbitals and the infrared vibration spectra show that the molecular defect makes the charge distributions of highest occupied moleculer orbital concentrated mainly in the molecule near the defect, and the C–H and N–N bond energies decrease. For the defective system, some molecules around vacancy have large vibration amplitude towards the vacancy direction. This will be likely to cause hole to collapse and realize the conversion of energy. These characteristics indicate that the presence of molecular vacancy defect causes the energy band gap to decrease, the structures of the molecules near the defect become loose, the charge distribution increases and the reaction activity augments. When the defective system is loaded by external energy, the molecules near the defect are expected to be unstable. The C–H or N–N bonds in those molecules are more prone to rupture to cause chemical reaction and release of energy, which is expected to be responsible for the forming of “hot spot”. These results provide some basic micro-information about revealing the formation mechanism of “hot spots” caused by molecular vacancy defects
- PACS:
31.15.es (Applications of density-functional theory (e.g., to electronic structure and stability; defect formation; dielectric properties, susceptibilities; viscoelastic coefficients; Rydberg transition frequencies)) 71.20.-b (Electron density of states and band structure of crystalline solids) 78.30.-j (Infrared and Raman spectra) [1] Bouma R H, Duvalois W, van der Heijden A E 2013 J. Microscopy 252 263
[2] LaBarbera D A, Zikry M A 2013 J. Appl. Phys. 113 243502
[3] Guo F, Zhang H, Hu H Q, Cheng X L 2014 Chin. Phys. B 23 046501
[4] Peng Y J, Liu Y Q, Wang Y H, Zhang S P, Yang Y Q 2009 Acta Phys. Sin. 58 655 (in Chinese) [彭亚晶, 刘玉强, 王英惠, 张淑平, 杨延强 2009 物理学报 58 655]
[5] Wang W T, Hu B, Wang M W 2013 Acta Phys. Sin. 62 060601 (in Chinese) [王文亭, 胡冰, 王明伟 2013 物理学报 62 060601]
[6] Boyd S, Murray J S, Politzer P 2009 J. Chem. Phys. 131 204903
[7] Schackelford S A 2008 Central Europ. J. Energ. Mater. 5 75
[8] Brill T B, James K 1993 Chem. Rev. 93 2667
[9] Walley S M, Field J E, Greenaway M W 2006 Mater. Sci. Technol. 22 402
[10] Duan X H, Li W P, Pei C H, et al. 2013 J. Mol. Model. 19 3893
[11] Margetis D, Kaxiras E, Elstner M, Frauenheim T, Manaa M R 2002 J. Chem. Phys. 117 788
[12] Brown J A, LaBarbera D A, Zikry M A 2014 Model. Simul. Mater. Sci. Eng. 22 055013
[13] Liu Z C, Wu Q, Zhu W H, Xiao H M 2015 Phys. Chem. Chem. Phys. 17 10568
[14] Kuklja M M, Kunz A B 1999 J. Phys. Chem. B 103 8427
[15] Kuklja M M, Kunz A B 2000 J. Phys. Chem. Solids 61 35
[16] Kuklja M M, Stefanovich E V, Kunz A B 2000 J. Chem. Phys. 112 3417
[17] Tsai D H 1991 J. Chem. Phys. 95 7497
[18] Kuklja M M 2014 Adv. Quantum Chem. 69 71
[19] Kuklja M M, Kunz A B 2000 J. Appl. Phys. 87 2215
[20] Rice B M, Chabalowski C F 1997 J. Phys. Chem. A 46 8720
[21] Choi C S, Prince E 1972 Acta Cryst. B 28 2857
[22] Cheng H P, Dan J K, Huang Z M, Peng H, Chen G H 2013 Acta Phys. Sin. 62 163102 (in Chinese) [程和平, 但加坤, 黄智蒙, 彭辉, 陈光华 2013 物理学报 62 163102]
[23] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865
[24] Whitley V H 2005 Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed. Matter Baltimore, Maryland, USA, July 31-August 5, 2005 p1357
[25] Pan Q, Zheng L 2007 Chin. J. Energ. Mater. 15 676 (in Chinese) [潘清, 郑林 2007 含能材料 15 676]
期刊类型引用(7)
1. 彭亚晶，孙爽，刘伟娜，刘宇辉. 冲击加载下环三亚甲基三硝胺的初始动态响应及反应机理. 物理学报. 2021(15): 298-306 . 
百度学术2. 杭贵云，余文力，王涛，王金涛，苗爽. 奥克托今/3-硝基-1, 2, 4-三唑-5-酮共晶炸药晶体缺陷的分子动力学研究. 兵工学报. 2019(01): 49-57 . 百度学术3. 杭贵云，余文力，王涛，王金涛，苗爽. 分子动力学法研究掺杂缺陷对HMX/NQ共晶炸药性能的影响. 火炸药学报. 2019(02): 145-151 . 百度学术4. 金韶华，李土娟，王雨乔，陈煜，张晓鹏，王俊峰，李领弟. 重结晶LLM-105的热危险性分析. 安全与环境学报. 2019(03): 854-861 . 百度学术5. 苗爽，王涛，王玉玲，杭贵云，戚春保，鲁昌兵. 晶体缺陷对HMX基PBX性能影响的理论计算. 含能材料. 2019(08): 636-643 . 百度学术6. 苗爽，张雷，王涛，王玉玲，杭贵云，梅宗书. RDX杂质对HMX性能影响的分子动力学研究. 含能材料. 2018(10): 828-834 . 百度学术7. 苗爽，王涛，王玉玲，曹智，夏琦. 掺杂缺陷对PBX性能影响的分子动力学研究. 固体火箭技术. 2018(06): 727-731+739 . 百度学术其他类型引用(0)
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[1] Bouma R H, Duvalois W, van der Heijden A E 2013 J. Microscopy 252 263
[2] LaBarbera D A, Zikry M A 2013 J. Appl. Phys. 113 243502
[3] Guo F, Zhang H, Hu H Q, Cheng X L 2014 Chin. Phys. B 23 046501
[4] Peng Y J, Liu Y Q, Wang Y H, Zhang S P, Yang Y Q 2009 Acta Phys. Sin. 58 655 (in Chinese) [彭亚晶, 刘玉强, 王英惠, 张淑平, 杨延强 2009 物理学报 58 655]
[5] Wang W T, Hu B, Wang M W 2013 Acta Phys. Sin. 62 060601 (in Chinese) [王文亭, 胡冰, 王明伟 2013 物理学报 62 060601]
[6] Boyd S, Murray J S, Politzer P 2009 J. Chem. Phys. 131 204903
[7] Schackelford S A 2008 Central Europ. J. Energ. Mater. 5 75
[8] Brill T B, James K 1993 Chem. Rev. 93 2667
[9] Walley S M, Field J E, Greenaway M W 2006 Mater. Sci. Technol. 22 402
[10] Duan X H, Li W P, Pei C H, et al. 2013 J. Mol. Model. 19 3893
[11] Margetis D, Kaxiras E, Elstner M, Frauenheim T, Manaa M R 2002 J. Chem. Phys. 117 788
[12] Brown J A, LaBarbera D A, Zikry M A 2014 Model. Simul. Mater. Sci. Eng. 22 055013
[13] Liu Z C, Wu Q, Zhu W H, Xiao H M 2015 Phys. Chem. Chem. Phys. 17 10568
[14] Kuklja M M, Kunz A B 1999 J. Phys. Chem. B 103 8427
[15] Kuklja M M, Kunz A B 2000 J. Phys. Chem. Solids 61 35
[16] Kuklja M M, Stefanovich E V, Kunz A B 2000 J. Chem. Phys. 112 3417
[17] Tsai D H 1991 J. Chem. Phys. 95 7497
[18] Kuklja M M 2014 Adv. Quantum Chem. 69 71
[19] Kuklja M M, Kunz A B 2000 J. Appl. Phys. 87 2215
[20] Rice B M, Chabalowski C F 1997 J. Phys. Chem. A 46 8720
[21] Choi C S, Prince E 1972 Acta Cryst. B 28 2857
[22] Cheng H P, Dan J K, Huang Z M, Peng H, Chen G H 2013 Acta Phys. Sin. 62 163102 (in Chinese) [程和平, 但加坤, 黄智蒙, 彭辉, 陈光华 2013 物理学报 62 163102]
[23] Perdew J P, Burke K, Ernzerhof M 1996 Phys. Rev. Lett. 77 3865
[24] Whitley V H 2005 Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed. Matter Baltimore, Maryland, USA, July 31-August 5, 2005 p1357
[25] Pan Q, Zheng L 2007 Chin. J. Energ. Mater. 15 676 (in Chinese) [潘清, 郑林 2007 含能材料 15 676]
期刊类型引用(7)
1. 彭亚晶，孙爽，刘伟娜，刘宇辉. 冲击加载下环三亚甲基三硝胺的初始动态响应及反应机理. 物理学报. 2021(15): 298-306 . 百度学术2. 杭贵云，余文力，王涛，王金涛，苗爽. 奥克托今/3-硝基-1, 2, 4-三唑-5-酮共晶炸药晶体缺陷的分子动力学研究. 兵工学报. 2019(01): 49-57 . 百度学术3. 杭贵云，余文力，王涛，王金涛，苗爽. 分子动力学法研究掺杂缺陷对HMX/NQ共晶炸药性能的影响. 火炸药学报. 2019(02): 145-151 . 百度学术4. 金韶华，李土娟，王雨乔，陈煜，张晓鹏，王俊峰，李领弟. 重结晶LLM-105的热危险性分析. 安全与环境学报. 2019(03): 854-861 . 百度学术5. 苗爽，王涛，王玉玲，杭贵云，戚春保，鲁昌兵. 晶体缺陷对HMX基PBX性能影响的理论计算. 含能材料. 2019(08): 636-643 . 百度学术6. 苗爽，张雷，王涛，王玉玲，杭贵云，梅宗书. RDX杂质对HMX性能影响的分子动力学研究. 含能材料. 2018(10): 828-834 . 百度学术7. 苗爽，王涛，王玉玲，曹智，夏琦. 掺杂缺陷对PBX性能影响的分子动力学研究. 固体火箭技术. 2018(06): 727-731+739 . 百度学术其他类型引用(0)
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