S高掺杂对锐钛矿TiO_2电子结构和红移影响的第一性原理研究

First-principles Study of Effect of Electronic Structures and Red-shift on Heavy S-doping Anatase TiO_2

基于密度泛函理论框架下的第一性原理平面波超软赝势方法,建立了未掺杂单胞和两种不同掺杂S原子浓度的锐钛矿TiO2模型,分别对模型进行了几何结构优化、态密度分布、能带分布、差分电荷密度分布、集居数和吸收光谱的计算.结果发现:掺杂后O原子2p态、S原子3p态和Ti原子3d态在导带内发生了强烈的杂化耦合作用,Ti原子3d态的电子向S原子3p态转移,引起导带下移;O原子2p态和S原子3p态在价带中杂化耦合作用,引起价带上移,引起了带隙变窄发生红移现象,同时,高掺杂S原子浓度越高红移越显著,计算结果与实验结果相一致.

In order to investigate the effect of heavy S-doping on the electronic structure of anatase TiO2,and to discover the mechanism of its band gap narrowed after S-doping,we carry out first-principles studies based on density-functional theory（DFT） for anatase TiO2 system.We study the band structures,densities of states,difference to the electron density,population analysis and spectrum of absorption.The result shows that after S-doping,a strong hybrid coupling would happen at the conduction band（CB） area of S atoms 3p orbit,O atoms 2p orbit and Ti atoms 3d orbit,which would lead to electrons of Ti atoms on the 3d orbit moving to 3p orbit of S atoms,conduction band becoming lower,and valence band arising becoming raise.Band gap would become narrow and the red shift electrophoresis would happen.Moreover,the effect of red shift increases with the concentration of S atoms increasing.The result of experiment is agreement with the theoretical result.