P₆团簇结构和性质的理论研究以及FC（O）O自由基与NO反应机理的量子化学研究

【作者】 赵江；

【导师】 曾祥华；

【作者基本信息】 扬州大学 ， 凝聚态物理， 2007， 硕士

【摘要】 纳米材料和技术是纳米科技领域最富有活力、研究内涵十分丰富的学科分支,纳米材料在整个新材料的研究应用方面占据着核心的位置。原子团簇(cluster)是构成纳米块体、薄膜、多层膜以及纳米结构的基本单元之一,对它的基态结构、能级和电子特性的理论研究是新材料微观结构设计中的重要课题之一,对于“订做”具有特定性能的新材料意义重大。本文主要采用量子力学中密度泛函(DFT) B3LYP方法,对P6团簇的几何构型、电子结构进行了计算。在此基础上对P6团簇的稳定性、能级分布和热力学性质变化规律进行系统地研究。与此同时,用密度泛函理论研究了FC(O)O自由基与NO作用的微观机理,并对反应通道进行了详细阐述。本论文主要包括以下三个部分:1、采用量子化学HF, B3LYP和MP2方法,选用6-31G*,6-311G*,cc-pVDZ和cc-pVTZ基组,对P6团簇的8种异构体进行了优化,并对它们的几何构型、稳定性、电子结构和振动频率进行了讨论,比较P6团簇各种异构体的稳定性以及导电性。研究表明:根据异构体的相对能量,P6异构体最稳定的构型c具有C2v对称性,而最不稳定的构型h具有D3h对称性,不同方法和基组所得到的稳定性大小基本一致,稳定性大小顺序为:c > f > a > d > e> g> b > h,并且得到结构g的导电性最好。2、采用密度泛函理论(DFT)B3LYP方法,在6-311G*基组水平下,对P6团簇的8种异构体进行了优化,并对它们的几何构型、能级分布和热力学性质进行了分析,讨论了最高占据轨道(HOMO)与最低空轨道(LUMO)之间的能级间隙(Eg),分析了团簇的化学活性。结果表明:团簇基态的HOMO能级和LUMO能级均为负值,团簇易得电子,构型g的能隙(Eg)最小,化学活性较强。最后求得结构c热力学性质与温度的关系。3、用密度泛函理论(DFT)的B3LYP方法,在6-311G(d,p)基组水平上研究了FC(O)O自由基与NO反应的微观机理,全参数优化了反应过程中各反应物、中间体、过渡态和产物的几何构型,在CCSD(T)水平上计算了它们的能量,振动分析结果证实了中间体和过渡态的真实性,从对FC(O)O与NO的反应机理的研究结果看,FC(O)O与NO反应为4条反应通道多步反应过程,其反应的主要通道是FC(O)O+NO→M3→TS6→M5→FNO+CO2,其主要产物是自由基FNO和CO2,与文献结果较为吻合。更多还原

【Abstract】 The nanometer material and technology is the most alive subject branch, with very abundant research connotation in the nanometer of scientific and technological fields, and nanometer material is occupying central position in research application of the whole new material. The atomic cluster is one of the elementary cell which forms nanometer body, membrane,multilevel membrane and nanometer structure, so the theoretical research for ground-state structures, energy level distribution and electronic properties of its is one of the important subject in the design of micro structure of new material, and has great signification in "custom-made"new material with specific performance. In this paper, the geometries and electronic structures of P6 clusters have been calculated by use of the density function theory (DFT)Becke 3LYP method. On this basis, the stabilities, energy levels and thermodynamic properties of P6 clusters are researched systematically. Moreover, Density function theory is performed to study the reaction mechanism of the reaction of FC(O)O with NO.The main contents are the following:1、Based on HartreeFock(HF), B3LYP of density functional theory(DFT) and second order perturbation theory MP2 method with basis set of 6-31G*, 6-311G*, cc-pVDZ and cc-pVTZ, we studied eight kinds of P6 clusters and discussed the geometries, stabilities,electronic structures and vibrational frequencies of the isomers. Then we compared the stabilities and the electrical conductivities of P6 isomers. The results indicate that the most stable c is C2v group,and the most unstable h is D3h group by comparing the relative energies of different isomers, the stability for P6 isomers derived by every methods at every levels is almost consistent,the order of stabilitiy for P6 isomers are c > f > a > d > e> g> b > h, and we also find the g has the best electrical conductivity.2、Based on B3LYP of density functional theory(DFT) method with basis set of 6-311G*, we study eight kinds of P6 clusters and discuss the geometries, energy levels,thermodynamic properties of the isomers. Then the HOMO-LUMO gaps and the chemical activation of P6 clusters are investigated.The results show that the HOMO and LUMO of the ground states of P6 clusters are negative, the Eg of the structure g is narrower, and the chemical activation strengthens. Finally,we get the relationships of thermodynamic functions with temperature about the c isomer.3、Density function theory was performed to study the reaction mechanism of the reaction of FC(O)O with NO. The geometric configurations of reactants , intermediates , transition states and products were optimized by B3LYP method at 6-311G(d,p) level. The energies of stationary points along the pathway were calculated at CCSD(T) level. Intermediates and transition states were confirmed by the results of vibrational analysis. From the results of the reaction mechanism of the reaction of FC(O)O with NO , one can see that the reaction of FC(O)O+NO has four pathways and several steps. Comparing the four pathways’activation energies, one can find that the pathway FC(O)O+NO→M3→TS6→M5→FNO+CO2 is the main reaction pathway and FNO radical and CO2 are the main products , which is in good agreement with literature.更多还原