C掺杂金红石相TiO2的电子结构和光学性质的第一性原理研究

运用第一性原理的局域密度近似+U(0 ≤U≤9 eV)方法研究了本征金红石相TiO₂在不同U值(对Ti-3d电子)下的禁带宽度、晶体结构以及不同比例C元素掺杂的金红石相TiO₂的电子结构和光学性质, 研究表明, TiO₂的禁带宽度和晶格常数随着U值的增加而增大. 综合考虑取U=3 eV并对其计算结果进行修正. 对于掺杂体系, 发现C 元素的掺杂在金红石相TiO₂中引入杂质能级, 杂质能级主要由O-2p轨道和C-2p轨道耦合形成, 杂质能级的引入可以增加TiO₂对可见光的响应, 从而使TiO₂的吸收范围增大. C原子掺杂最佳比例为8.3%, 此时光学吸收边的红移程度最明显, 可增大光吸收效率, 从而提高了TiO₂光催化效率.

Electronic structure and optical properties of C doped rutile TiO2: the first-principles calculations

The lattice parameters and band-gap of native rutile TiO₂ are investigated by the first-principles calculations of local density approximation+U method with different U values for Ti-3d (0 ≤U≤ 9 eV). The electronic structures and optical properties of different content C doped rutile TiO₂ systems are also studied by the same method with appropriate U values. The calculations results show that the lattice parameters and band-gaps of TiO₂ increase with the increase of U and the U =3 eV is fitted for the corrected band-gap. For the doped systems, the impurity energy level is introduced due to the coupling between O-2p and C-2p, which can increase the TiO₂ absorption edge to the visible region, and therefore enlarge the absorption region of TiO₂. Moreover, the 8.3% C is an optimal doped density, which can lead to the red-shift of optical absorption edge obviously and increase the coefficient of light absorption, therefore facilitate the enhancement of the photocatalytic efficiency.