摘要
基于密度泛函理论(DFT)的第一性原理模守恒赝势方法,对纯金红石型TiO_2和Ti、O两种空位缺陷相的几何结构、能带结构、态密度(DOS)以及光学性质进行了系统地对比研究。结果发现,含有空位缺陷的TiO_2键长增大,原子布局值减小并出现微弱的磁性;空位缺陷导致导带变窄,导带和价带都向低能级方向移动,由空位原子贡献的载流子增强了体系的电导率,费米能级上移进入导带;与纯金红石型TiO_2的直接带隙宽度(3.0eV)相比较,Ti空位缺陷相转变为P型半导体且直接带隙为1.816eV,而O空位缺陷相转变为n型半导体且间接带隙为1.961eV。同时,两种空位缺陷结构的介电峰显著红移,折射率有明显变化,对可见光区的吸收系数均比纯TiO_2高。与O空位结构相比,Ti空位结构的介电常数、折射率、消光因子和对可见光的吸收强度更大,更能增强电子在低能端的光学跃迁,具有更佳的可见光催化性能。
The crystal structures,band structures, density of states and optical properties of Ti and O va- cancies in rutile TiO2 in comparision with those of pure rutile TiO2are investigated,by using the first- principles based on density functional theory （DFT） method and the norm conserving pseudopotential scheme. The obtained results show that both vacancy-doped structures exhibit a weak magnetism, and a larger bond length and atomic population for TiO bond. The conduction band gaps decrease and both conduction and valence bands move towards the low energy direction in the vacancy-doped structures, and the contribution of atomic vacancy carriers thus enhances the electrical conductivity of the system. By introducing vacancies in rutile TiO2, the Ti-vacancy phase shows a p-type semiconducting nature with energy gap of 1. 816 eV, and the O-vacancy phase shows an n-type semiconducting nature with energy gap of 1. 961 eV. Meanwhile,the dielectric peaks of the vacancy-doped structures display a significant red shift,and possess a higher absorption coefficient than that of pure TiO2 in the visible region. Compared with O-vacancy structure, the larger dielectric constant, refractive index and extinction factor for visible light absorption intensity in Ti-vacancy structure would enhance the optical transitions for low-energy e- lectrons and possess better catalytic properties of visible light.
出处
《光电子．激光》
EI
CAS
CSCD
北大核心
2017年第11期1224-1232,共9页
Journal of Optoelectronics·Laser
基金
国家自然科学基金(11547247
11704007)
陕西省科技攻关计划(2014K08-17)
陕西省科学技术研究发展计划(2016JM1012
2016JM1016)
陕西省教育厅科研计划(15JK1043)
宝鸡市科技攻关计划(14GYGG-5-2)
宝鸡文理学院重点科研(ZK16033
YK1615)资助项目
