【作者】 邱玲；

【导师】 肖鹤鸣；

【作者基本信息】 南京理工大学 ， 材料学， 2007， 博士

【摘要】 运用当代理论和计算化学方法，主要是量子力学（QM）和分子动力学（MD）方法，对多系列氮杂环硝胺类高能衍生物的结构和性能，进行了较为系统的计算和模拟。从气相分子、固态晶体至复合材料（高聚物粘结炸药），完成了寻求高能量密度化合物（HEDC）和高能量密度材料（HEDM）的全过程研究。通篇包括三部分内容：第一部分是HEDC的“气相”分子设计。基于量子化学计算，建议和运用判别HEDC的定量标准（密度ρ≈1.9g／cm³，爆速D≈9.0km／s和爆压P≈40.0 GPa），并兼顾其稳定性要求（热解引发键离解能BDE＞84 kJ／mol），从上述多系列标题物中推荐了几十种HEDC。建议并证明了一种基于量子化学计算、较方便准确地预测高能化合物晶体密度的新方法。选择已有实验晶体密度的45种硝胺类爆炸物为研究对象，运用量子化学多种方法和多种基组的计算，求得它们分子的（按0.001 e／Bohr³等电子密度面包围体积所定义的）理论密度(ρ_cal)，通过与实验晶体密度(ρ_exp)相比较，发现第一性原理DFT-B3LYP方法结合6-31G^**水基组水平的结果(ρ_cal)与ρ_exp良好相符。将理论计算所得密度(ρ_cal)和生成热，代入Kamlet-Jacobs方程求得爆速（D）和爆压（P），形成了定量评估HEDC的有效手段。在DFT-B3LYP／6-31G^**水平下求得多硝基氮杂环己烷和多硝基氮杂环戊烷两类单环硝胺的全优化构型、红外光谱和200～800 K温度范围的热力学性质；预测它们的理论晶体密度(ρ_cal)、爆速（D）和爆压（P）。以UB3LYP／6-31G^**方法求得四种可能热解引发步骤的BDE，确定热解引发机理为N-NO₂键均裂并以此判别相对稳定性。发现1，2，4-三硝基三氮杂环己烷、1，3，5-三硝基三氮杂环己烷（即RDX）和1，2，4，5-四硝基四氮杂环己烷符合前述HEDC的能量和稳定性标准。对双环-HMX同系物和TNAD同分异构体作如上类似的结构-性能关系研究。根据判别HEDC的定量标准兼顾稳定性要求，发现双环-HMX及其衍生物中Ⅱ-3～Ⅱ-5、Ⅳ～Ⅶ和Ⅹ值得予以推荐；TNAD及其同分异构体尽管爆轰性能稍逊，但当N-NO₂基处于对位和间位时稳定性超过RDX，可作为高能钝感炸药推荐。对系列三环硝胺衍生物结构和性能的研究为新型HEDC分子设计增添了信息和规律。在双环-HMX两个稠合五元环中插入环丁烷爆轰性能下降，而在双环-HMX或TNAD等双环硝胺中增加环杂硝胺稠合数目则使爆轰性能提高；把三环硝胺转变为相应环脲硝胺其氧平衡和爆轰性能得以改善。HHTD（六硝基六氮杂三环十二烷）和HHTDD（六硝基六氮杂三环十二烷二酮）的椅式和船式构象能量特性很高，但稳定性稍差。报导了系列螺环硝胺化合物的B3LYP／6-31G^**全优化分子几何，基于电子结构参数预测了热力学稳定性；求得红外光谱和200～800 K温度范围的热力学性质；估算了理论晶体密度、生成热、爆热、爆速和爆压：通过比较四种可能的热解引发键（C-C、C-N、N-N和N-NO₂）的离解能和热解反应活化能，揭示其热解引发机理。将分子稳定性或感度与静态和动态电子结构参数相关联。按HEDC的定量标准和稳定性要求，推荐TNSHe（四硝基四氮杂螺己烷）、TNSH（四硝基四氮杂螺庚烷）和TNSO（四硝基四氮杂螺辛烷）作为具较高开发和应用价值的HEDC目标物。对系列呋咱和氧化呋咱稠环硝胺衍生物结构和性能的类似计算研究表明，后者的密度、爆热、爆速和爆压均比相应的前者高。当分子中仅含一个对二硝基哌嗪和两个呋咱环时，即能满足HEDC的定量要求；随分子中呋咱环变为氧化呋咱环或对二硝基哌嗪稠合数目增多，密度和爆炸性能均逐渐增大，远超过HEDC的定量标准：但环上N-O键较弱，导致稳定性下降，使开发应用受到限制。第二部分选择双环-HMX和TNAD为研究对象，首次对它们的晶体能带结构和性能进行周期性量子化学（QM）计算和分子动力学（MD）模拟研究，探讨了压强和温度的影响。运用CASTEP程序包中固体密度泛函方法计算能带结构。证明了LDA／CA-PZ方法较GGA／PBE和GGA／PW91方法对双环硝胺分子型晶体更为适用。首次报导了双环-HMX和TNAD的晶体结构、分子结构、电荷分布、前沿能带、带隙和态密度及其与导电性和感度等性能的关联；分析Fermi能级附近导带和价带的组成，预示热解引发键为N-NO₂键，与由实验或气相分子热解机理计算导出的结论相一致。双环-HMX的带隙比TNAD的大，预示前者稳定性大于后者，与气相分子热解引发反应活化能和热解引发键离解能计算所导致的结论相一致，也符合“最易跃迁原理”。加之双环-HMX的能量特性较好，故而建议特别关注和加强双环-HMX的应用开发研究。报导了压强（P）对双环-HMX和TNAD晶体结构和性能的影响：P＜10 GPa时二者的能带和电子结构参数变化较小；P=10～400 GPa时，这些参数变化较大；当P＞400GPa时，二者的带隙接近为零，DOS成连续曲线，显现了金属属性。运用Material Studio程序包中DISCOVER模块，对双环-HMX和TNAD晶体的广义结构和性能进行了5～400 K温度范围的NPT-MD模拟研究。证明了COMPASS力场的适用性。观察到晶体结构、热膨胀性能和力学性能随温度而递变的规律：二者的晶胞参数和体积均随温度升高而线性递增；线膨胀系数和体膨胀系数均随温度升高略有减少；弹性系数和模量随温度升高而下降，表明刚性减弱，延展性下降。双环-HMX的泊松比大于TNAD，表明前者的塑性大于后者。前者的晶格能约为后者的2倍，表明前者比后者稳定。晶体研究表明，双环-HMX更具研究开发价值。第三部分运用MD方法模拟研究了双环-HMX和TNAD基高聚物粘结炸药（PBX）的结构和性能。考察了粘结剂种类和含量及其沿基炸药不同晶面添加等因素对PBX力学性能、结合能和爆轰性能的影响，为高能复合材料亦即为HEDM的实际配方设计提供信息、奠定基础。采用Material Studio程序包中“切割分面”方法，将双环-HMX和TNAD超晶胞沿（001）、（010）和（100）三个不同晶面方向切割，并将四种典型氟聚物粘结剂：聚偏二氟乙烯（PVDF）、聚三氟氯乙烯（PCTFE）、氟橡胶(F₂₃₁₁)和氟树脂(F₂₃₁₄)分别置于双环-HMX和TNAD三种晶面上，然后依次对所得12种PBX模型进行COMPASS力场下的MD模拟，求得它们的广义结构和性能。首次报导了双环-HMX和TNAD基PBX的力学性能、结合能和爆轰性能及其随氟聚物粘结剂种类和含量以及晶面不同而递变的规律：少量氟聚物粘结剂的加入明显改善基炸药的力学性能，对双环-HMX不同晶面力学性能的改善效果为（010）＞（001）≈（100），对TNAD为（001）＞（010）＞（100）；以双环-HMX（010）／F₂₃₁₄和TNAD（001）／PVDF的综合力学性能相对较好。各氟聚物与双环-HMX和TNAD（010）晶面之间的相互作用均较（100）和（001）晶面强；相同百分含量的氟聚物与双环-HMX和TNAD各晶面之间的相互作用均为PVDF＞F₂₃₁₁＞F₂₃₁₄＞PCTFE。少量氟聚物虽使双环-HMX和TNAD的爆炸性能有所下降，但仍较常用炸药TNT高得多，故所得PBXs仍不失为具较高开发和应用价值的高能复合材料。总之，本文基于量子化学发展了一套计算高能物质密度（ρ）、爆速（D）和爆压（P）以及热解引发键离解能（BDE）的简易方法，建议了判别HEDC的能量和稳定性相结合的定量标准，在多系列氮杂环硝胺类高能衍生物结构-性能系统计算研究的基础上，找到了几十种潜在的HEDC目标物，并特别推荐开发高能钝感双环-HMX。首次运用固体密度泛函理论和分子动力学（MD）方法，计算和模拟研究了以双环-HMX和TNAD为典型的晶体结构-性能及其随压强和温度而递变的规律；对双环-HMX和TNAD为基的多种高聚物粘结炸药（PBX）的结构和性能首次进行MD模拟，为优选粘结剂和HEDM配方设计提供了示例和丰富信息。这些工作在HEDC／HEDM多学科交叉前沿研究领域中，具有开拓性和原始创新性，较好地完成了国家“973”和国家自然科学基金等项目赋予的各项应用基础科研任务。更多还原

【Abstract】 The present dissertation is devoted to systematic research on the structures andproperties of multi-series of the cyclic nitramine energetic compotmds by using moderntheoretical and computational chemistry methods, mainly including quantum mechanics（QM） and molecular dynamics （MD）. From the gas molecules, the crystals, and to thecomposite materials （such as polymer-bonded explosives）, the whole study process ofsearching for high energy density compounds （HEDCs） and high energy density materials（HEDMs） has been completed. The whole work can be divided into three parts:The first part concentrates on "gas" molecular design for HEDC. Based on the QMcalculations, the quantitative criteria of detonation performance as a HEDC （densityρ≈1.9 g/cm³, detonation velocity D≈9.0 km/s, and detonation pressure P≈40.0 GPa） andthe stability requirement （bond dissociation energy of the initial step in thermolysis BDE＞84 kJ/mol） are employed to recommend several decades of potential HEDC objectivesfrom the title compounds.Based on the QM computations, a novel method for conveniently and exactlypredicting the crystalline densities of energetic compounds is proposed and testified. 45energetic nitramines with experimental crystalline densities are selected for research, andtheir molecular densities (ρ_cal, defined as inside a contour of 0.001 e/Bohr³ density) wereobtained from the calculations of different QM methods and basis sets. In comparison withthe experimental densities (ρ_exp), it is found that the results (ρ_cal calculated by the hybriddensity functional theory （DFT） B3LYP method with the 6-31G^** basis set agree wellwith the experiments. Based on the predicted densities (ρ_cal and heats of formation, thedetonation velocity （D） and detonation pressure （P） of the energetic compounds areestimated by the Kamlet-Jacobs formula, which establishes a novel way to quantitativelyevaluate the HEDC.The fully optimized structures, infrared （IR） spectra, and thermodynamic properties(C°_p,m, S°_m and H°_m) in the temperature range 200～800 K of two types of monocyclicnitramines polynitroazacyclohexane and polynitroazacyclopentane are obtained at theDFT-B3LYP/6-31G^** level. Theoretical crystal density （ρ）, detonation velocity （D）, anddetonation pressure （P） of each compound are predicted. Bond dissociation energies （BDE）of four possible trigger bonds in their thermolyses are computed by the B3LYP/6-31G^**method under the unrestricted Hartree-Fock model, and their pyrolysis mechanisms areascertained to be the homolysis of N-NO₂ bond. Relative stabilities of these monocyclic nitramines are also judged from the BDE. It is found that 1,2,4-trinitrotriazacyclohexane,1,3,5-trinitrotriazacyclohexane i.e. RDX, and 1,2,4,5-tetranitrotetraazacyclohexane agreewith the forementioned quantitative criteria of a HEDC and stability requirement.Similar studies are performed on the bicyclo-HMX derivatives and TNAD isomers.According to the quantitative criteria of a HEDC and stability requirement, it is found thatbicyclo-HMX and its derivatives （Ⅱ-3～Ⅱ-5,Ⅳ～Ⅶ, andⅩ） are worth recommendation aspotential candidates of HEDCs. Although the detonation properties of TNAD and itsisomers are not large enough, the isomers with N-NO₂ groups at the meta- andpara-positions have better stabilities than RDX. Thus, they can be recommended asenergetic insensitive explosives.The studies on the structures and properties of some tricyclic nitramines provide basicinformation and discipline for the molecular design of novel HEDCs. The results show thatadding a cyclobutane between two cyclic nitramines of bicyclo-HMX results in detonationproperties decreasing much in comparison with bicyclo-HMX, while increasing thenumber of combined cyclic nitramines in bicyclo-HMX and TNAD will improve theirdetonation performances markedly. When changing the tricyclic nitramines into thecorresponding glycoluril derivatives, the oxygen balance and detonation performanceimprove remarkably. The chair and boat conformations of hexanitrohexaazatricyclododecane （HHTD） and hexanitrohexaazatricyclododecanedione （HHTDD） have excellentexplosive performance, but their stabilities are less satisfied.The fully optimized structures of a series of spiro nitramines are reported, and theirthermodynamic stabilities are evaluated according to the electronic structures. The IRspectra and thermodynamic properties (C°_p,m, S°_m, and H°_m) in the temperature range200～800 K are computed. Their crystalline densities, heats of formation, detonationvelocities, and detonation pressures are predicted. Pyrolysis mechanisms of the spironitramines are investigated and ascertained by comparing the BDE of four possible triggerbonds （C-C, C-N, N-N and N-NO₂） and the activation energies （Ea） in the thermolysis.The molecular stability or sensitivity of spiro nitramines is correlated well with their staticand dynamic electronic structures. According to the quantitative criteria of HEDCs andstability demand, TNSHe （tetranitrotetraazaspirohexane）, TNSH （tetranitrotetraazaspiroheptane）, and TNSO （tetranitrotetraazaspirooctane） are recommended as HEDCcandidates with superior exploitation and application values.Similar calculations have also been performed on a series of furazan andfuroxan-fused cyclic nitramines to study their structures and properties. The results indicate that all of the furoxan-fused cyclic nitramines have largerρ, Q, D, and P than thecorresponding furazan-fused cyclic nitramines. When the molecule only contains onep-dinitropiperazine and two furazan rings, it has met the quantitative demand of a HEDC.With changing the furazan into the furoxan or the number of fused p-dinitropiperazineincreasing, density and detonation properties all increase and exceed the HEDC’squantitative criteria much. However, the N-O bond in the furazan or furoxan ring is weakerin comparison with other energetic compounds, which leads the Stabilities of furazan andfuroxan-fused cyclic nitramines to decrease and hence restricts their exploitations andapplications.The second part focuses on theoretical studies of bicyclo-HMX and TNAD. Periodicquantum mechanics （QM） calculations and molecular dynamics （MD） simulations are firstcarried out to study their crystalband structures and properties. The influences of pressureand temperature on the structures and properties have also been investigated.The density functional theory （DFT） methods in the CASTEP program package areused to compute the crystal band structures. The results demonstrate that LDA/CA-PZ ismore proper and satisfactory than GGA/PBE and GGA/PW91 for studying the bicyclicnitramine molecular crystals. Crystal structure, molecular structure, charge distribution,frontier band structure, band gap, and density of states （DOS） of bicyclo-HMX and TNADare first reported. The correlations between various parameters and their conductivity,sensitivity are discussed in detail. An analysis of the valence and conduction bands showsthat the N-NO₂ bond is the trigger bond during their thermolyses, which are consistentwith the conclusions drawn from the experiments and theoretical studies on the thermolysismechanism of molecules in the gas phase. Bicyclo-HMX with larger band gap is morestable than TNAD, which is consistent with the conclusions drawn from the activationenergies （Ea） and BDE, and also accord with "the principle of the easiest electrontransition" （PET）. Considering the superior detonation performances of bicyclo-HMX, wesuggest that much more attention should be particularly paid to the bicyclo-HMX, andexploitation and application researches about it should be intensified. Moreover, theinfluence of pressure on the crystal structures and properties of bicyclo-HMX and TNADhas also reported. Their band structures and electronic structures change scarcely as thepressure less than 10 GPa, while in the pressure range of 10～400 GPa these parameterschange largely. When the pressure is larger than 400 GPa, the band gaps of both them areclose to zero and the DOS almost becomes a continuum curve, showing a metalliccharacter. Applying the DISCOVER module of Materials Studio （MS） 3.0.1 software package,periodic NPT-MD simulations in the temperature range of 5～400 K are performed onbicyclo-HMX and TNAD to study their general crystal structures and properties.Applicability Of the COMPASS force field is demonstrated. The effects of temperature onthe crystal structures, thermal expansion, and mechanical properties of bicyclo-HMX andTNAD are observed. Their lattice parameters and cell volume all increase linearly with theincreasing temperature, while the linear and volume expansion coefficients decreaseslightly as the temperature increases. Elastic constants and mechanical moduli all decreasewith the increasing temperature, indicating that the system’s rigidity weakens andductibility decreases. Bicyclo-HMX has the larger Poisson ratio than TNAD, showing thatthe former has lager plasticity than the latter. The lattice energy of bicyclo-HMX is nearlytwice as much as that of TNAD, implying the former is more stable than the latter. Thecrystalline studies indicate that bicyclo-HMX has more exploitation and application values.The third part centers on the MD simulations of the structures and properties ofbicyclo-HMX and TNAD-based polymer bonded explosives （PBXs）. The effects of thetype and content of polymer binders and its orientation along different crystalline surfaceson the PBXs’ mechanical properties, binding energies, and detonation performances areinvestigated. These provide information and establish the basis for the practicalformulation design of energetic composite materials, namely HEDM.The "cutting surface" method as implemented in the MS program package is chosento cleave the bicyclo-HMX and TNAD supercells along three different crystalline surfaces（001）, （010）, and （100）. Four types of typical fluorine polymer binders PVDF, PCTFE,F₂₃₁₁, and F₂₃₁₄ are then put on above three crystalline surfaces of bicyclo-HMX and TNAD,respectively, and a dozen of bicyclo-HMX and TNAD-based PBX models are obtained,respectively. MD simulations are carried out on them with the COMPASS force field toget their general structures and properties. Mechanical properties, binding energies,detonation performances, and the discipline of them changing with the type and content ofpolymer binders and different crystalline surfaces are first reported for the bicyclo-HMXand TNAD-based PBXs. The results show that the mechanical properties of the basalexplosives can be effectively improved by adding small amounts of fluorine polymers. Theeffects of improvement on different crystalline surfaces of bicyclo-HMX are in the order of（010）＞（001）≈（100）, and those of TNAD are in the sequence of （001）＞（010）＞（100）.Considered various aspects comprehensively, the mechanical properties of the PBXsbicyclo-HMX（010）/F₂₃₁₄ and TNAD（001）/PVDF are better. The interactions between each fluorine polymer and different crystalline surfaces of bicyclo-HMX and TNAD alldecrease in the order of （010）＞（100）＞（001）, and those of the polymers with the samecontent decrease in the sequence of PVDF＞F₂₃₁₁＞F₂₃₁₄＞PCTFE. Detonation propertiesdecrease slightly compared with the pure crystal by the additions of small amounts offluorine polymers, but they are still superior to the commonly used explosive TNT andhence can be used as good energetic materials with high exploitation and applicationvalues.In a word, a set of convenient methods are developed in this thesis based on thequantum chemistry to compute the density （ρ）, detonation velocity （D）, detonation pressure（P）, and bond dissociation energy （BDE） of energetic compounds. According toquantitative criteria of energy and stability demand for a HEDC, a series of potentialHEDC targets are recommended among various series of cyclic nitramine derivativesbased on the systematic theoretical studies on their structures and properties, and theinsensitive energetic compound bicyclo-HMX is especially recommended to exploit. Theperiodic DFT and classical MD methods are first employed to calculate and simulate thecrystal structures and properties of typical bicyclic nitramines: bicyclo-HMX and TNAD.The disciplines of the changing of structures and properties with the pressure andtemperature are investigated. MD method is also used to simulate the structures andproperties of bicyclo-HMX and TNAD-based PBX with various polymer binders ondifferent crystal surfaces, which provide a demonstration and plentiful information forchoosing optimal polymer binders and formulation design of HEDM. These studies areprecursory and originally innovative in front of multi-subject crossing research fields ofHEDC/HEDM, and successfully complete the scientific research tasks of basicapplications assigned by the national "973" projects and National Natural ScienceFoundations.更多还原