【作者】 张竹霞；

【导师】 许并社；

【作者基本信息】 太原理工大学 ， 材料学， 2010， 博士

【摘要】 新型炭材料的特性几乎可涵盖地球上所有物质的性质甚至相对立的两种性质,从最硬到极软、全吸光-全透光、绝缘体-半导体-高导体、绝热-良导热、高铁磁体、高临界温度的超导体等。纳米炭材料会表现出特异的光、电、磁、热、力学、机械等性能,成为当前世界科学研究的热点。基于密度泛函理论的第一性原理方法因其不依赖于经验参数而成为凝聚态物理、量子化学和材料科学中的主要研究手段。本论文对一些不同维度的新型纳米碳基材料,如:富勒烯,碳纳米管,石墨烯等进行了第一性原理的研究。研究内容如下:（1）使用密度泛函理论分别研究了符合和不符合五元环最大分离规则（IPR）的Tb₃N@C₈₄一系列异构体的结构和电子性质。结果表明笼上存在一对毗邻的五元环的不符合IPR规则的结构具有最大的能隙,显示出最好的动力学稳定性;满足IPR规则的Tb₃N@C₈₄化合物具有最好的热力学稳定性。Tb3N与C84之间的作用力主要是离子键,并且在费米面上Tb₃N@C₈₄较C84有大的电子分布,说明Tb3N的嵌入可以增强笼的导电性。（2）使用B3LYP/6-31G（d）方法对有机太阳电池中作为电子受体材料的富勒烯衍生物苯基C61丁酸甲酯（[60]PCBM）的同分异构体进行了计算。PCBM与C60通过六元环和六元环共用的C=C双键加成得到的产物是热力学控制产物;通过五元环和六元环共用的C-C键加成得到的产物则是动力学控制产物。[60]PCBM与C₆₀的第一绝热电子亲和势很接近。PCBM对前线轨道贡献很小,[60]PCBM的最高占据分子轨道（HOMO）和最低非占据分子轨道（LUMO）的电子云主要分布在笼上。PCBM提升了C₆₀的LUMO能级水平,有利于提高太阳能电池光电转化效率。自然布居分析表明PCBM与笼之间没有发生显著的电荷转移。所有的研究表明PCBM基团并不涉及电池光电转换的过程,但在调整C₆₀能级水平提高光电转换效率中发挥了重要作用。使用同样的方法也研究了[70]PCBM,得到了相同的规律。（3）通过第一性原理研究了Ag在碳管内壁的吸附和在管端修饰羧基和羟基基团上负载的情况。计算结果表明Ag可以被稳定的吸附在管内壁,在一定的直径范围内,这种吸附能力随着直径的增加而增加。对于Ag负载在修饰-COOH和-OH基团后的SWCNT上时,-COOAg的稳定性要高于-OAg。无论是单修饰-COOH或-OH基团,还是共修饰-COOH和-OH基团,只有第一个Ag是被稳定地化学吸附,之后吸附的Ag主要以物理吸附的形式负载在碳管的表面。这也从侧面说明实验中Ag离子在修饰后碳管中的负载主要以物理吸附为主。（4）使用密度泛函理论研究了修饰或掺杂Au原子后石墨烯（graphene）与半胱氨酸结合的能力和性质。Au-S之间化学键的作用增强了graphene与半胱氨酸之间的结合力。使用Au原子修饰或掺杂graphene,可增加graphene基底与半胱氨酸之间的电子转移,较多的电子转移改变了graphene基底费米能级附近的性质,改变了graphene的电导性质。计算结果表明Au原子修饰或者掺杂的graphene是一种潜在的检测半胱氨酸的传感器材料,会在检测富含半胱氨酸的金属硫蛋白等生物领域得到广泛的应用。本文也对Pt掺杂的graphene进行了研究,结果表明它也是一种好的半胱氨酸传感器材料。更多还原

【Abstract】 The characteristics of new-carbon materials cover all the natures of substances, even the opposite ones from the hard to very soft, all absorption and all transmission, insulator - semiconductor - high conductor, insulation - good thermal conductivity, high ferromagnet, high critical temperature superconductors, etc. Owing to their novelty in optical,electronic,magnetic,thermal,or mechanic properties, carbon nanomaterials have attracted intensive research interest.Because of the independence of empirical parameters, the first principle study has become the main research means in condensed matter physics, quantum chemistry and materials science. In this paper, some novel materials with different dimensions,such as fullerene,nanotube,and graphene,were studied on the basis of the first principles calculations.The results are summarized as follows:（1） The geometric and electronic structures of fullerenes encapsulating trimetallic nitride cluster Tb₃N@C₈₄ were studied using the density functional theory. Geometric optimization showed that Tb₃N@C₈₄ that violates the Isolated-Pentagon Rule （IPR） with a pentalene unit formed by fused pentagon pair is the most kinetically stable isomer with the largest energy gap. Compared to IPR-violating Tb₃N@C₈₄ isomers, IPR-Tb₃N@C₈₄ is the most thermodynamically favorable endohedral compound with the lowest energy. The interaction between Tb3N and C84 is ionic and Tb₃N@C₈₄ has a higher density of states （DOS） than empty C84 molecule at the Fermi energy, indicating that the embedment of Tb3N unit can increase the conductance of C84.（2） The electronic parameters of fullerenes are essential for their potential use as active layers in organic solar cells. Two isomeric forms of [60] PCBM （phenyl-C61-butyric acid methyl ester） clusters were calculated using the B3LYP method with 6-31G（d） basis set. It has been found that the contraction of C6-6 double bonds is favorable for addition. The first Adiabatic Electron Affinity （AEA） for [60] PCBM is similar to that for C₆₀. The energy gaps between the highest-occupied molecular orbital （HOMO） and the lowest-unoccupied molecular orbital （LUMO） of [60] PCBM are reduced compared with C₆₀. PCBM derivatives show increased level of LUMO of fullerenes. From the natural charge populations, it was found that adding PCBM unit onto the C₆₀ cages does not change the charge populations remarkably; attaching a PCBM has no effects on the electronic structures of C₆₀. The results of theoretical calculation suppose that PCBM is not involved in the process of photoelectric conversion, but plays a key role in adjusting the level of HOMO-LUMO for increasing photoelectric conversion efficiencies. Similar results were also reached for [70]PCBM.（3） The first principles study was performed on the stability of Ag adsorbed on the internal walls of single-walled carbon nanotube （SWCNT） and loaded on acid modified SWCNT. The calculation results show that Ag can be adsorbed stably on the internal walls of SWCNT. The adsorption energy increases as the diameter in a certain range. Ag can also be loaded on the modified SWCNT surface in the form of–COOAg and-OAg groups, and -COOAg group is more stable than -OAg group. For either tne adsorption on the inner SWCNT or the load on the modified SWCNT surface, only a small part of the Ag ions can be stably bonded to the wall of SWCNT. In other word, most of Ag ions observed in experiments are loaded or adsorbed on CNT by physical adsorption.（4） The adsorption of cysteine molecule on intrinsic and Au-doped or decorated graphene sheets was studied by density functional theory calculations. Compared with the intrinsic graphene, Au-doped or decorated graphene strongly adsorbs cysteine molecules with high binding energy value and short distance between the cysteine molecules and the graphene surface. The calculation of electron transfers and dipole moment supports the notion that Au doping or decorating influences the electronic properties of graphene substantially. Furthermore, the density of states results show the orbital hybridization between cysteine and Au-doped or decorated graphene sheet. Therefore, the calculations suggest that Au-doped or decorated graphene is a promising candidate for sensor detecting a variety of S-containing proteins and metalloenzymes. Pt-doped graphene sheets are also studied and the same conclusion was obtained.更多还原