【作者】 刘丽；

【导师】 付佳；

【作者基本信息】 西华大学 ， 物理学， 2023， 硕士

【摘要】 与晶体结构不同,非晶体中的原子或分子在空间上呈现出短程有序和长程无序的不规则排列。这种并非完全无序或有序的结构导致非晶体呈现出与晶体不同的物理和化学性质,比如玻璃的导电性、聚合物的玻璃化转变等,因此在生活和生产中得到了大量的关注和应用。本文以xCuO-（68-x）TeO₂-V₂O₅玻璃和PαMS聚合物为例,通过高阶微扰法、分子动力学模拟等多种手段,研究了不同物理化学因素,比如温度、浓度以及玻璃化转变等与典型非晶物质的局域结构及其动力学行为之间的关系,为更好地理解和利用相关非晶体物质提供了理论和数据支持。主要研究内容和结果如下:（1）研究了成分浓度对局域分子结构的影响。利用具有四角拉伸畸变的八面体络合物高阶微扰公式,定量分析了xCuO-（68-x）TeO₂-V₂O₅（x=5、10、20和30mol%）玻璃中Cu²⁺的自旋哈密顿参量和局域结构,立方晶场参量（D_q）、归一化因子（N）、相对伸长率（ρ）、芯极化常数（κ）和轨道缩减因子（H）等参数随CuO含量呈非线性变化。当x=10mol%CuO时,[CuO₆]^10-基团因Jahn-Teller效应产生了0.1%的相对四角伸长,当x=30mol%CuO时,畸变程度最大,部分Cu²⁺还原为Cu⁺,Z轴方向氧空位出现的概率增加,即部分[CuO₆]^10-基团转变为[CuO₄]^6-基团,铜的配位数从原来的6个减少到4个。（2）研究温度、聚合度以及玻璃化转变对局域分子结构及动力学行为的影响。首先利用经典分子力场模拟了不同分子量PαMS聚合物材料的玻璃化转变（Tg）温度,发现当分子体系的聚合度增加时,聚合物的玻璃化转变温度升高,但增加的速度减慢。然后采用分子反应力场模拟了PαMS材料的热解过程,分析了其热解机理,并通过径向分布函数、原子均方根位移和相关系数对模拟结果进行分析表征,探究了其温度、升温速率和分子量以及玻璃化转变对局域分子结构的动态变化影响。发现,在升温过程中,分子结构发生巨大变化,主链C-C键更容易断裂,产物主要以C₉H₁₀单体形式呈现;原子的径向分布函数受到温度高低的影响大于升温速率;主链相邻C-C键之间的相关系数呈现负相关,随着温度的增加而减小,在玻璃化转变温度附近某些C-C键的相关系数会出现反常现象。更多还原

【Abstract】 Unlike the structure of a crystal,the atoms or molecules in an amorphous structure exhibit an irregular arrangement of short-range ordered and long-range disordered in space.This structure,which is not completely disordered or ordered,leads to the physical and chemical properties of amorphous crystals that are different from those of crystals,such as the electrical conductivity of glass,the glass transition of polymer,etc.,so it has received a lot of attention and application in life and production.Taking xCuO-（68-x）TeO₂-V₂O₅ glass and PαMS polymer as examples,the relationship between different physical and chemical factors,such as temperature,concentration and glass transition,and the local structure and dynamic behavior of typical amorphous materials is studied by means of high-order perturbation method and molecular dynamics simulation,which provides theoretical and data support for better understanding and utilization of related amorphous materials.The main research contents and results are as follows:（1）The spin Hamiltonian parameters and local structure of Cu²⁺in x CuO-（68-x）TeO₂-V₂O₅（x=5,10,20 and 30 mol%）glasses are quantitatively analyzed by using the high-order perturbation formula of octahedral complex with tetrahedral tensile distortion.The cubic crystal field （D_q）,the normalization factor（N）,the relative elongation（ρ）,the core polarization constant（κ） and the orbital reduction factor（H）show nonlinear changes with the content.When x=10 mol% CuO,the [CuO₆]^10- group produces a relative tetragonal elongation of 0.1% due to the Jahn-Teller effect.When x=30 mol% CuO,the degree of distortion is the greatest,part of Cu²⁺ is reduced to Cu⁺,and the probability of oxygen vacancy increases along the z-axis,reducing the coordination number of copper from the original 6 to 4,and the[CuO₆]^10- group is replaced by the [CuO₄]^6-group.（2）The effects of temperature,degree of polymerization and glass transition on the local molecular structure and the corresponding kinetic behavior were investigated.Firstly,the glass transition temperature（Tg）of PαMS polymer with different molecular weight was simulated by the classical molecular force field.It was found that the glass transition temperature of the polymer increased when the degree of polymerization of the molecular system increased,but the increase rate slowed down.Then,the pyrolysis process of PαMS material was simulated by molecular reaction force field,and its pyrolysis mechanism was analyzed.The simulation results were characterized by radial distribution function,root mean square displacement of atoms and correlation coefficient,and the dynamic changes of temperature,heating rate,molecular weight and glass transition on the local molecular structure were investigated.It was found that during the temperature rise,the molecular structure changed greatly,the C-C bond of the main chain was more easily broken,and the product was mainly in the form of C₉H₁₀monomer.The radial distribution function of atoms is influenced more by temperature than by heating rate.The correlation coefficients between adjacent C-C bonds of the main chain show a negative correlation and decrease with the increase of temperature.The correlation coefficients of some C-C bonds will show abnormal phenomena near the glass transition temperature.更多还原