论文总字数：21722字

摘 要

本课题利用基于密度泛函理论的第一性原理方法，采用CASTEP 程序，计算锐钛矿相TiO₂晶体及其存在氮掺杂和氧空位缺陷时的电子结构，并分析其能带结构、态密度和轨道结构，揭示缺陷对锐钛矿相TiO₂电子结构的影响。

几何结构优化结果表明，锐钛矿相纯TiO₂的晶格常数与实验测量所得结果非常接近，说明我们此处所采用的计算方法是合理的，结果可靠；掺杂前后对比发现N取代O后对长键影响最大。能带分析结果表明，完整锐钛矿二氧化钛的带隙为2.157eV，N掺杂后出现杂质使得带隙变小；氧空位的出现，使得TiO₂晶体费米能级由价带顶部移动到了导带顶部。态密度分析表明，完整TiO₂晶体的导带中Ti 3d态占主导地位，价带主要是由O 2p态构成；N掺杂后在导带和价带之间出现了一个独立的峰，提高了可见光吸收的效果，使得其光催化性能增强；含O空位锐钛矿TiO₂体系的态密度组成不变，只是使得态密度向低能处偏移。轨道分析表明，完整锐钛矿二氧化钛晶体中电子呈现定域状态均匀的分布在O和Ti原子周围；N掺杂后价带顶的电子轨道主要定域在N 2p周围，O空位后价带顶电子轨道主要定域在O空位周围呈三角形分布，顶点指向三个Ti。

关键字：锐钛矿二氧化钛 第一性原理 氮掺杂 氧空位

The Electronic Structure of Defect Anatase TiO₂ Crystal

Abstract

Based on this study the use of first-principles density functional theory, using CASTEP program that calculates the phase anatase TiO₂ crystal and electronic structure and the presence of nitrogen-doped vacancy defects, and analyze its energy band structure, density and track structure, as well as phase defects affect the electronic structure of anatase TiO₂.

Geometry optimization results show that the lattice constant of the experimental results obtained measurements of pure anatase TiO₂ is very close , indicating that the calculation method we used here are reasonable, results are reliable; before and after comparison found N doped after replace O greatest impact on the long bond. The results showed that the analysis of band, complete TiO₂ band gap of 2.157eV, after N doping impurities makes the band gap becomes smaller; oxygen vacancy occurs, so that TiO₂ crystals Fermi level to move from the top of valence band to the top of conduction band. State density analysis showed complete conduction band TiO₂ crystals in Ti 3d states dominated in the valence band is mainly composed of O 2p states; N doping between the conduction and valence bands there is a independent peak, the effect of improving the absorption of visible light, so that the photocatalytic performance enhancements; O vacancy density of states containing anatase TiO₂ system of constant composition, just make shift to a lower energy state density. Orbital analysis shows that complete anatase titanium dioxide crystals in electron delocalization state presented evenly distributed around the O and Ti atoms ; N-doped electron orbit after the top of the valence band is mainly localized around the N 2p, N doping conduction band electron orbitals no significant change in the distribution of the relative reduction in the contribution of the electron distribution in the conduction band; O vacancy after the price with the top electronic tracks mainly localized triangular distribution, the apex point in space around three Ti .

Key words : Anatase TiO₂; ab initio; N-doped; O-vacancy

目录

摘要 I

Abstract II

第一章 绪论 1

1.1 TiO₂性质 1

1.2 TiO₂应用 1

1.3 TiO₂光催化机理 2

1.4 TiO₂掺杂改性研究 4

1.5研究目的和意义 4

第二章 第一性原理计算及研究方法 5

2.1 第一性原理计算简介 5

2.1.1 密度泛函理论 5

2.1.2 交换关联能泛函 6

2.2 Materials studio-CASTEP 计算程序 8

2.3 结构分析技术 9

2.3.1能带结构 9

2.3.2晶体结构 9

2.3.3态密度 9

2.4 研究内容 10

第三章 计算结果及数据分析 11

3.1 模型构造与计算方法 11

3.2计算结果和分析 12

3.2.1几何结构优化分析 12

3.2.2 能带结构分析 13

3.2.3 态密度分析 15

3.2.4 轨道分析 17

第四章 结论及展望 20

4.1 结论 20

4.2 展望 20

参考文献 22

致谢 24

第一章 绪论

1.1 TiO₂性质

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