摘要
In this work, we perform DFT ＋ U periodic calculations to study geometrical and electronic structures and oxygen vacancy formation energies of SmxCayCe1-x-yO2-δ systems （x = 0.0312, 0.0625, 0.125 and 0.250; y = 0.0312, 0.0625, 0.125 and 0.250; δ = 0.0312, 0.0625, 0.125, 0.250 and 0.50） with different oxygen vacancy and doping concentrations. The calculated results show that the VI-Sm3＋-V2 structures where there is a position relationship of the face diagonal between V1 and V2 both nearest to Sm3＋ have the lowest energy configurations. The study on electronic structures of the SmxCayCe1-x-yO2-δ systems finds that excess electrons arise from oxygen vacancies and are localized on f-level traps of their neighbor Ce, and Ca2＋ and Sm3＋ co-doping effectively restrains the reduction of Ce4＋. In order to avoid the existence of Ce3＋, x and y must be both larger than 0.0625 as δ = 0.125 or δ must be smaller than 0.125 as x = y = 0.0625. The Ce3＋/Ce4＋ change ratio k has an obvious monotonous increase with increasing the vacancy oxygen concentration. The introduction of Sm3＋ decreases k. In addition, the doped Sm3＋ can restrain the reduction of Ce4＋ when the V1-Sm3＋-V2 structure with a face diagonal position relationship in lower reduced atmosphere exists. It need be pointed out that the Sm025Ce07501.5 system should be thought of as a Sm-doped Ce2O3 one.
In this work, we perform DFT ＋ U periodic calculations to study geometrical and electronic structures and oxygen vacancy formation energies of SmxCayCe1-x-yO2-δ systems （x = 0.0312, 0.0625, 0.125 and 0.250; y = 0.0312, 0.0625, 0.125 and 0.250; δ = 0.0312, 0.0625, 0.125, 0.250 and 0.50） with different oxygen vacancy and doping concentrations. The calculated results show that the VI-Sm3＋-V2 structures where there is a position relationship of the face diagonal between V1 and V2 both nearest to Sm3＋ have the lowest energy configurations. The study on electronic structures of the SmxCayCe1-x-yO2-δ systems finds that excess electrons arise from oxygen vacancies and are localized on f-level traps of their neighbor Ce, and Ca2＋ and Sm3＋ co-doping effectively restrains the reduction of Ce4＋. In order to avoid the existence of Ce3＋, x and y must be both larger than 0.0625 as δ = 0.125 or δ must be smaller than 0.125 as x = y = 0.0625. The Ce3＋/Ce4＋ change ratio k has an obvious monotonous increase with increasing the vacancy oxygen concentration. The introduction of Sm3＋ decreases k. In addition, the doped Sm3＋ can restrain the reduction of Ce4＋ when the V1-Sm3＋-V2 structure with a face diagonal position relationship in lower reduced atmosphere exists. It need be pointed out that the Sm025Ce07501.5 system should be thought of as a Sm-doped Ce2O3 one.
基金
Supported by the National Natural Science Foundation of China(No.51474133)
Inner Mongolia Natural Science Foundation(No.2016MS0513)
