GGA+U方法研究不同浓度Cr掺杂对TiO_(2)的磁性和光学性质的影响

GGA + U method to study the effect of different concentration of Cr doping on the magnetic and optical properties of TiO_(2)

本文采用基于第一性原理的GGA+U方法,计算研究了本征态锐钛矿TiO_(2)和不同浓度Cr掺杂锐钛矿TiO_(2)(1/8、1/16、1/32 )的电子结构、磁性及光学性质. 计算结果表明:所有掺杂体系中Ti_(0.9375) Cr_(0.0625) O_(2)的结合能最小,因此Ti_(0.9375) Cr_(0.0625) O_(2)体系的稳定性要高于Ti_(0.875) Cr_(0.125) O_(2)、Ti_(0.96875) Cr_(0.03125) O_(2)体系;Cr元素的掺入导致掺杂后体系发生晶格畸变,这有利于光生空穴和电子对的分离,提高其光催化性能;同时,由于Cr-3d和O-2p电子相互作用,使得掺杂体系呈现出铁磁性质,并且随着掺杂浓度的增加会使体系具有更好的铁磁性质;掺杂体系与本征TiO_(2)相比,掺杂后吸收带边均发生红移,光谱响应范围变大;并且随掺杂浓度的增加,光响应范围也在增大,从而有效增强了体系对于可见光的吸收能力.

The electronic structure, magnetic properties and optical properties of anatase TiO_(2)and Cr doped anatase TiO_(2)(1 / 8, 1 / 16, 1 / 32 ) were studied by first principles GGA + U method.The calculation results show that the binding energy of Ti_(0.9375) Cr_(0.0625) O_(2)is the smallest in all doping systems. Therefore, the stability of Ti_(0.9375) Cr_(0.0625) O_(2)system is higher than that of Ti_(0.875) Cr_(0.125) O_(2)and Ti_(0.96875) Cr_(0.03125) O_(2),the doping of Cr leads to lattice distortion, which is beneficial to the separation of photogenerated holes and electron pairs, and improves the photocatalytic performance. At the same time, because of the interaction of Cr-3d and O-2p electrons, the doped system presents ferromagnetic properties, and with the increase of doping concentration, the system will have better ferromagnetic properties.Compared with the intrinsic TiO_(2), the absorption band edge of the doped system is red shifted and the spectral response range is enlarged,Moreover, with the increase of doping concentration, the light response range also increases, which effectively enhances the absorption ability of the system for visible light.