稀土(La/Ce/Pr/Nd)掺杂锐钛矿相TiO_2磁性及光催化活性的第一性原理研究

采用密度泛函理论下的平面波赝势方法,建立了未掺杂锐钛矿TiO_2和La/Ce/Pr/Nd单掺杂的锐钛矿TiO_2模型.几何优化后,通过计算形成能分析了掺杂结构的稳定性;通过自旋电子态密度的计算分析了各个掺杂模型的磁性状态,并采用比较磁性基态能量的方法对分析结果加以验证;讨论了各稀土元素掺杂对锐钛矿能带结构和吸收光谱的影响.结果表明:La/Pr掺杂的锐钛矿TiO_2具有亚铁磁性,Nd掺杂的锐钛矿具有反铁磁性,Ce掺杂锐钛矿为顺磁体;Ce掺杂对锐钛矿能带结构影响较小,吸收光谱红移不明显,而La/Nd掺杂则能有效提升锐钛矿对可见光的吸收系数,Pr掺杂能使锐钛矿TiO_2在红外光区出现吸收峰.

First-principle study of the magnetism and photocatalyticactivity of RE(La/Ce/Pr/Nd) doping anatase TiO2

The models of pure TiO₂ and La/Ce/Pr/Nd singly doped TiO₂ are established by using the plane wave potential based on density functional theory. After geometry optimization, the stability of the mixed structure is analyzed by calculating the formation energy. Then the magnetic state of each doped model is analyzed by calculating the spin electronic state density. The analyses are verified by comparing magnetic ground state energies. Finally the influences of each rare earth element on band structure and absorption spectrum of TiO₂ are discussed. The results show that La/Pr doped TiO₂ presents ferromagnetism, Nd doped TiO₂ exhibits anti-ferromagnetism, and Ce doped TiO2 is paramagnetic body. The band structure of TiO₂ is affected less because Ce is doped and the red shift of absorption spectrum is not obvious. While visible light absorption coefficient of TiO₂ is effectively improved because La/Nd is doped. Pr doped TiO₂ manifests an absorption peak in the infrared region. If the electronic structure is considered in the further calculation research, one should make sure what magnetic state the system is in and whether there is spin-electron band splitting effect firstly. In order to obtain the correct results, the influence of the band structure should not be ignored.