对不同掺杂浓度La^(3+)∶PbWO_4晶体电子结构的研究

Study on the electronic structures of La^(3+)∶PbWO_4 with different doping levels

采用缺陷化学方法讨论了PbWO4晶体中不同浓度掺La3+时可能存在的缺陷团簇模型.通过GULP计算软件模拟计算了缺陷团簇中La3+离子最可能的替位位置,并通过基于密度泛函理论的离散变分DV Xα方法计算得到相应的La3+∶PWO4晶体的电子态密度.计算得到低浓度掺杂时晶体的禁带宽度变宽,高浓度掺杂时晶体的禁带宽度变窄.实验测得低浓度掺La3+时晶体的吸收边紫移,高浓度掺La3+时晶体的吸收边红移,计算结果与实验结果相符.计算表明,La3+∶PWO4晶体中掺La3+可以有效地抑制420 nm吸收.

The possible defect models of La^3 ＋ ： PbWO4 with different doping levels were discussed by defect chemistry and the most possible substitutonal positions of the impurity La^3＋ ions were studied using the general utility lattice program （GULP）. The electronic structure of the La^3＋ ： PbWO4 with the most possible La^3 ＋ substitution model was calculated using the DV-Xa method. The calculated results predicate that the energy gap of the crystal will be broadened under light doping level and will be narrowed under heavy doping level as compared with that of the un-doped crystal, which coincide with the experimental results. The calculation also predicates that the doping of La^3 ＋ can effectively restrict the 420 nm absorption band.