运用第一性原理方法研究了Cu/Ag单掺及Cu-Ag共掺对ZnO稳定性、电子结构和光学性质的影响。CuZn2和CuZn1-CuZn3的形成能接近0.0 eV, CuZn1-CuZn2的形成能为负值, 表明Cu较易掺杂且掺杂时有聚集的趋势。AgZn2的形成能为2.5 eV, AgZn1-AgZn2和AgZn1-AgZn3的形成能高于4.5 eV, 说明高浓度的Ag掺杂在实际合成中不易出现。CuZn1-AgZn2和CuZn1-AgZn3的形成能与AgZn2的相近。CuZn2、CuZn1-CuZn2和CuZn1-CuZn3模型的Cu3d与O2p轨道有较大程度的杂化, 价带顶端主要由Cu3d轨道占据。AgZn2、AgZn1-AgZn2和AgZn1-AgZn3模型的Ag4d与O2p轨道杂化较弱, 价带顶端主要由O2p轨道占据。CuZn1-AgZn2和CuZn1-AgZn3模型的Cu3d与O2p轨道虽有杂化, 但价带顶端主要由O2p轨道占据。Cu或Ag原子掺杂使Zn4s轨道在导带区显著向下移动, 降低了模型的带隙宽度, 它们对ZnO电子结构的影响主要集中在带隙附近。Cu-Ag共掺修饰ZnO电子结构的能力介于Cu和Ag单掺之间。上述掺杂模型吸收边都发生了红移, 实现了ZnO对可见光的吸收, 同时对3.10~3.90 eV范围内紫外光的吸收均高于纯ZnO, 有效提高了ZnO的光催化效率。结合形成能分析可知, 在不同类型掺杂下最有利的光催化模型分别为CuZn1-CuZn2、AgZn2和CuZn1-AgZn2。

The stability, electronic structure and optical properties of ZnO with Cu/Ag doped and Cu-Ag codoped were studied by first-principles method. Formation energies of CuZn2 and CuZn1-CuZn3 are close to 0.0 eV, and negative for CuZn1-CuZn2, which indicates that Cu doped is effortless and tends to gather. The value for AgZn2 is 2.5 eV, and higher than 4.5 eV for AgZn1-AgZn2 and AgZn1-AgZn3. It’s difficult for Ag doping with higher concentration. Formation energies of CuZn1-AgZn2 and CuZn1-AgZn3 are close to that of AgZn2. The Cu3d and O2p states have obvious hybridization in models of CuZn2, CuZn1-CuZn2 and CuZn1-CuZn3, the top of valence band is mainly occupied by Cu3d states. The hybridization between Ag4d and O2p states for AgZn2, AgZn1-AgZn2 and AgZn1-AgZn3 models is weaker, the top of valence band is mainly occupied by O2p states. For CuZn1-AgZn2 and CuZn1-AgZn3 models, although Cu3d states hybridize with O2p states, the top of valence band is mainly occupied by O2p states. Cu/Ag doped and Cu-Ag codoped lead Zn4s states downward significantly, which reduces the band gap of above models. They influence the electronic structure of ZnO near the band gap mainly. The modified ability of Cu-Ag codoped to ZnO electronic structure is between Cu/Ag doped ZnO. The absorption edges of above models have obvious red-shift, which realizes the visible light absorption for ZnO. The ultraviolet light absorption also is higher than pure ZnO in the range of 3.10-3.90 eV. Cu/Ag doped and Cu-Ag codoped improves the photocatalytic activity of ZnO. According to formation energy analysis, the models with higher photocatalysis under different doping are CuZn1-CuZn2, AgZn2 and CuZn1-AgZn2.