本文選題：含能材料 + 分子晶體�。� 參考：《大連理工大學(xué)》2015年博士論文

【摘要】：含能材料(EMs),包括炸藥、推進(jìn)劑和煙火劑等,已廣泛應(yīng)用于國民經(jīng)濟(jì)和國防工業(yè)等各個(gè)領(lǐng)域。因此,含能材料的基礎(chǔ)研究對(duì)國民經(jīng)濟(jì)的增長和國防工業(yè)的發(fā)展都有著重要的意義。由于含能材料的實(shí)驗(yàn)研究具有一定的危險(xiǎn)性,計(jì)算機(jī)模擬逐漸成為含能材料研究的重要手段之一。本文基于密度泛函理論,并結(jié)合分子動(dòng)力學(xué)模擬,分別研究了分子晶體中分子間相互作用,金屬有機(jī)物骨架聚合物含能材料的晶體結(jié)構(gòu)、電子結(jié)構(gòu)和彈性性質(zhì),以及新型鈍感炸藥FOX-7晶體在常壓和高壓下的熱解行為。目前,大部分含能材料屬于分子晶體,分子晶體中分子間的相互作用決定了其晶體結(jié)構(gòu)及其物理化學(xué)性質(zhì)描述的準(zhǔn)確性。然而,基于局域密度近似或者廣義梯度近似的密度泛函理論由于不能描述長程關(guān)聯(lián)相互作用,不能很好地描述分子晶體中的相互作用。為了能更好地描述分子間相互作用,人們已經(jīng)發(fā)展了多種方案來彌補(bǔ)密度泛函理論框架下這些近似的缺陷。雖然人們對(duì)分子二聚體、分子團(tuán)簇等體系進(jìn)行了大量的測(cè)試,但是這些修正方案在描述分子晶體的表現(xiàn)卻知之甚少。本文系統(tǒng)地測(cè)試了密度泛函理論及其修正方案在描述分子晶體中相互作用時(shí)的表現(xiàn),為分子晶體的物理化學(xué)性質(zhì)及其動(dòng)力學(xué)性質(zhì)的研究提供可靠的方法指導(dǎo)。我們首先對(duì)甲烷晶體的結(jié)構(gòu)進(jìn)行了測(cè)試,發(fā)現(xiàn)通過加入經(jīng)驗(yàn)對(duì)勢(shì)來修正DFT的PBE-Grimme(PBE-D2)和PBE-D3方案可以很好地重復(fù)實(shí)驗(yàn)的晶格常數(shù)和晶格能,而且和標(biāo)準(zhǔn)DFT計(jì)算相比計(jì)算成本增加不明顯；而vdW-DF方案盡管可以給出合理的晶格常數(shù)和體彈性模量,但卻高估了甲烷晶體的晶格能,并且增加了計(jì)算成本。更進(jìn)一步,我們采用合作者針對(duì)包含C、H、N和O體系發(fā)展了DFT+LAP方案,計(jì)算了十二種分子晶體的晶格常數(shù)和晶格能。通過和實(shí)驗(yàn)值及PBE-Grimme的計(jì)算結(jié)果相對(duì)比,評(píng)估了此方案在描述分子間相互作用時(shí)的表現(xiàn)。結(jié)果表明,我們合作者發(fā)展的DFT+LAP得到的計(jì)算結(jié)果與實(shí)驗(yàn)值相符合,而且計(jì)算量也與DFT方案基本相當(dāng)；另一方面,PBE-Grimme方案是測(cè)試的所有方案中最好的,我們的計(jì)算結(jié)果與之相近。因此,DFT+LAP方案在研究分子晶體和其它非共價(jià)鍵相互作用體系時(shí)是一種高效且精確的計(jì)算方法。隨后,我們更進(jìn)一步改進(jìn)和發(fā)展了DFT+LAP方法,研究指出需要更有效的勢(shì)函數(shù)才可以更精確描述分子晶體中分子間的相互作用。和傳統(tǒng)炸藥相比,人們己經(jīng)合成出了高含氮量且具有更優(yōu)異的爆轟性能的金屬有機(jī)骨架聚合物(MOF),這類材料被證實(shí)為潛在的新型含能材料。金屬有機(jī)骨架聚合物的晶體結(jié)構(gòu)極其復(fù)雜,其電子結(jié)構(gòu)和力學(xué)性質(zhì)對(duì)這類潛在含能材料的應(yīng)用有著重要的影響。本文采用第一性原理方法系統(tǒng)地研究了一維、二維和三維MOF-EMs的晶體結(jié)構(gòu)、電子結(jié)構(gòu)和彈性性質(zhì)。我們首先對(duì)MOF-EMs的晶體結(jié)構(gòu)用PBE泛函及色散修正方案進(jìn)行測(cè)試。結(jié)果表明,PBE泛函明顯地低估了MOF-EMs晶體中的非共價(jià)鍵相互作用,從而高估了晶格常數(shù)。所有的修正方法都或多或少地修正了對(duì)分子晶體晶格常數(shù)的描述,但是一些方案如PBE-D和optB88-vdW卻過度修正這種效應(yīng)。在所有方案中,optPBE-vdW可以獲得與實(shí)驗(yàn)最一致的晶體結(jié)構(gòu)。電子結(jié)構(gòu)分析表明只有NHN為金屬,其余MOF-EMs為半導(dǎo)體或絕緣體。我們進(jìn)一步討論了MOF-EMs的電子結(jié)構(gòu)和其感度之間的關(guān)系,指出相似結(jié)構(gòu)的帶隙越大,MOF的沖擊感度越高,則MOF越不敏感,這和實(shí)驗(yàn)相符。此外,我們預(yù)測(cè)的MOF-EMs的體彈性模量介于15.1-35.0 GPa之間,高于傳統(tǒng)炸藥的體彈性模量。除了含能材料的基本性質(zhì),其爆轟機(jī)制的研究也是含能材料的研究熱點(diǎn)。FOX-7作為一種新型鈍感炸藥,理解其熱解機(jī)制不僅對(duì)FOX-7的儲(chǔ)藏、運(yùn)輸和應(yīng)用都有著重要的意義,還有助于新型鈍感炸藥的設(shè)計(jì)。本文采用第一性原理分子動(dòng)力學(xué)模擬研究了FOX-7晶體在常壓和高壓下的熱解過程。常壓熱解過程表明FOX-7的起始分解從C—NO2鍵的斷裂開始。我們?cè)敿?xì)地分析了熱解產(chǎn)物及其演化規(guī)律。結(jié)果表明熱解產(chǎn)物包含大量的N2、H2O,還包含少量的CO、CO2等。同時(shí)發(fā)現(xiàn)中間產(chǎn)物NO、NO2、OH等分子片段都攜帶電荷,這些帶電分子片段可能會(huì)促進(jìn)FOX-7的后續(xù)化學(xué)反應(yīng)。進(jìn)一步模擬壓力對(duì)熱解的影響指出壓力的增加并不直接對(duì)熱解機(jī)制產(chǎn)生影響,卻加快了熱解反應(yīng)發(fā)生的速率。
[Abstract]:The energetic materials (EMs), including explosives, propellants and pyrotechnics, have been widely used in various fields such as national economy and national defense industry. Therefore, the basic research of energetic materials is of great significance to the growth of national economy and the development of national defense industry. In this paper, based on the density functional theory and molecular dynamics simulation, this paper studies the intermolecular interaction in molecular crystals, the crystal structure, the electronic structure and the elastic properties of the energetic materials, as well as the new insensitive explosive FOX-7 crystal at normal pressure. At present, most of the energetic materials are molecular crystals, and the intermolecular interactions in molecular crystals determine the accuracy of their crystal structure and the description of their physical and chemical properties. However, the density functional theory based on local density approximation or generalized gradient approximation can not describe the interaction of long range correlation, The interaction in molecular crystals can not be well described. In order to better describe intermolecular interactions, a variety of schemes have been developed to compensate for these approximate defects in the framework of density functional theory. Although a large number of systems have been tested for molecular two polymer, molecular clusters and other systems, these modifications are described The expression of molecular crystal is little known. This paper systematically tests the performance of density functional theory and its modified scheme in describing the interaction of molecular crystals. It provides a reliable method for the study of the physicochemical properties and kinetic properties of molecular crystals. First, we have tested the structure of methane crystal and found that the structure of the crystal is tested. The lattice constant and lattice energy of the DFT PBE-Grimme (PBE-D2) and PBE-D3 schemes can be well repeated by adding the experience to the potential, and the increase of the computational cost is not obvious compared with the standard DFT calculation. While the vdW-DF scheme can give reasonable lattice constants and bulk modulus of elasticity, but it overestimates the lattice energy of the methane crystal. In addition, we used the collaborators to develop the DFT+LAP scheme for the C, H, N and O systems. We calculated the lattice constants and lattice energies of the twelve molecular crystals. By comparing the experimental values and the calculated results of PBE-Grimme, we evaluated the performance of this case in describing intermolecular interactions. It is clear that the calculated results obtained by our collaborators are in accordance with the experimental values, and the amount of calculation is similar to that of the DFT scheme; on the other hand, the PBE-Grimme scheme is the best of all the solutions of the test, and our calculation results are similar. Therefore, the DFT+LAP scheme is studying the interaction between the molecular crystal and other non covalent bonds. The system is an efficient and accurate method of calculation. Then, we have further improved and developed the DFT+LAP method. It is pointed out that more effective potential functions are needed to describe the intermolecular interactions in molecular crystals more accurately. Compared with traditional explosives, people have synthesized high nitrogen content and have better detonation properties. The metal organic skeleton polymer (MOF) can be proved to be a potential new energetic material. The crystal structure of the metal organic framework polymer is extremely complex. Its electronic structure and mechanical properties have an important influence on the application of this kind of potential energetic material. This paper systematically studies one dimension and two dimension by the first principle method. The crystal structure, the electronic structure and the elastic properties of the three-dimensional MOF-EMs. We first test the crystal structure of MOF-EMs by PBE functional and dispersion correction scheme. The results show that the PBE functional significantly underestimates the non covalent bond interaction in the MOF-EMs crystal and overestimates the lattice constant. All the correction methods are more or less repaired. The crystal lattice constants of molecular crystals are described, but some schemes, such as PBE-D and optB88-vdW, have overcorrected this effect. In all schemes, optPBE-vdW can obtain the most consistent crystal structure with the experiment. The electronic structure analysis shows that only NHN is metal and the rest MOF-EMs is half conductor or insulator. We further discuss the MOF-EMs The relationship between the electronic structure and its sensitivity indicates that the larger the band gap of the similar structure is, the higher the impact sensitivity of MOF is, the less sensitive the MOF is, which is in agreement with the experiment. In addition, the bulk modulus of the predicted MOF-EMs is between the 15.1-35.0 GPa and the bulk modulus of the traditional explosive. The research is also a hot spot of energy containing materials.FOX-7 as a new type of insensitive explosive. Understanding its pyrolysis mechanism is not only important for the storage, transportation and application of FOX-7, but also for the design of new insensitive explosives. In this paper, the heat of FOX-7 crystal under normal pressure and high pressure is studied by the first principle molecular dynamics model. The pyrolysis process at the normal pressure indicates that the initial decomposition of the FOX-7 begins with the fracture of the C NO2 bond. We have analyzed the pyrolysis products and their evolution rules in detail. The results show that the pyrolysis products contain a large number of N2, H2O, and a small amount of CO, CO2, etc., and that the intermediate products NO, NO2, OH, etc. carry charge, these charged molecules The section may promote the subsequent chemical reaction of FOX-7. Further simulation of the effect of pressure on pyrolysis indicates that the increase of pressure does not directly affect the pyrolysis mechanism, but accelerates the rate of the pyrolysis reaction.

【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB34

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