中文摘要：

本文利用第一性原理研究了In：Mn：LiNbO3晶体及对比组的电子结构和光学特性.研究结果显示,掺锰铌酸锂晶体的杂质能级主要由Mn的3d态轨道贡献,在禁带中处于较浅的位置,在价带顶端也有所贡献,晶体带隙较纯铌酸锂晶体变窄;Mn：LiNbO3晶体分别在1.66,2.85 eV等位置形成了吸收峰;掺In的Mn：LiNbO3晶体在1.66 eV附近的吸收明显减弱,掺铟浓度约为阈值（约3 mol%）时在1.66 eV吸收继续减弱,并出现了一些新的光吸收峰.本文提出了1.66 eV的吸收与Mn2＋离子相关,因掺铟离子而出现的2.13 eV的吸收与Mn3＋离子相关,这两峰随着掺铟离子的增加将出现前者减弱而后者增强的变化,该变化可以用电荷在锰、铟离子间的转移解释;还提出在铟、锰共掺铌酸锂晶体中,若光存储的记录光选择低能段（1.66 eV附近）,此时对应记录灵敏度要求较小的掺铟量等观点.

英文摘要：

The electronic structures and the absorption spectra of the indium and manganese codoped LiNbO3 crystals and their comparative groups are investigated by first-principles based on the density functional theory.The supercell crystal structures are established with 60 atoms,including four models：the near-stoichiometric pure LiNbO3 crystal（LN）,the manganese doped LiNbO3 crystal（Mn：LN,charge compensation model as MnLi＋-VLi-）,the indium and manganese codoped LiNbO3 crystal（In：Mn：LN,charge compensation model as InLi2＋-MnLi＋-3VLi-）,and the other indium and manganese codoped LiNbO3 crystal（In（E）：Mn：LN,charge compensation model as InLi2＋-InNb2--MnLi＋-VLi-）.The results show that the extrinsic defect levels within the forbidden band of Mn：LN crystal are mainly contributed by Mn 3d orbital electrons,which also affect the top of the valence band.The band gap of Mn：LN about 3.18 eV is narrower than that of LN;the band gaps of In：Mn：LN and In（E）：Mn：LN sample are 2.82 and 2.93 eV respectively.The electron density of state（DOS） of manganese codoped LiNbO3 crystal shows that the orbits of Mn 3d,Nb 4d and O 2p superpose each other,i.e.,forming covalent bonds,which result in conduction and valence bands shifting toward low energy.The indium ion does not contribute the extrinsic energy level within forbidden band,it affects the band gap through changing O2- electron cloud shape.The band gap narrows down if the indium ions occupy lithium ion positions,and becomes broad if the indium ions occupy niobium ion positions.It is found that the Mn：LN,In：Mn：LN and In（E）：Mn：LN samples display the absorption peaks at 3.25,3.11,2.97,2.85,2.13 and 1.66 eV.The last absorption peak is contributed by the electron transferring from the Mn2＋ energy level to conduction band,and the doping of indium ions leads to attenuation of this peak.The peak at 2.13 eV relates to the Mn3＋,it is enhanced by the doped indium ions.The indium ions in crystal would influence the absorption,wh