使用GGA+U方法研究了Ca O或Ba O与Sm2O3共掺杂Ce O2体系几何和电子结构及氧离子迁移。计算结果表明,Ba和Sm均靠近氧空位时Ba Sm Ce30O63体系最稳定;Sm靠近,Ca远离氧空位时Ca Sm Ce30O63体系最稳定。Ba Sm Ce30O63和Ca Sm Ce30O63体系中...使用GGA+U方法研究了Ca O或Ba O与Sm2O3共掺杂Ce O2体系几何和电子结构及氧离子迁移。计算结果表明,Ba和Sm均靠近氧空位时Ba Sm Ce30O63体系最稳定;Sm靠近,Ca远离氧空位时Ca Sm Ce30O63体系最稳定。Ba Sm Ce30O63和Ca Sm Ce30O63体系中均不存在Ce4+变价。对Ca Sm Ce30O63体系氧离子迁移的研究发现,当氧离子迁移到空位时,迁移能大小顺序为Em(3→V)<Em(1→V)<Em(4→V)<Em(2→V),这一规律源于氧离子与低价掺杂离子产生负电势之间的排斥作用;对Ba Sm Ce30O63体系氧离子迁移的研究发现,当空位迁移到周围氧离子时,迁移能大小顺序为Em(V→3)<Em(V→5)<Em(V→1),这一规律源于氧空位产生的正电势与低价掺杂离子产生的负电势之间的吸引作用。此外,Ca Sm Ce30O63体系最小迁移能小于Sm Ce31O63体系,证实了Ce O2-Sm2O3-Ca O体系离子电导率大于Ce O2-Sm2O3体系的实验结果。展开更多
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 = 0.0...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.展开更多
Influence of doping and oxygen vacancy concentrations on oxygen ion or oxygen vacancy(V)migration energies of SmxCe1-xO2-δ(x=0.0625,0.125,0.25 andδ=0.0625,0.125)systems using a GGA+U method are studied.Calculated re...Influence of doping and oxygen vacancy concentrations on oxygen ion or oxygen vacancy(V)migration energies of SmxCe1-xO2-δ(x=0.0625,0.125,0.25 andδ=0.0625,0.125)systems using a GGA+U method are studied.Calculated results show that advantage migration types change from V→O2-to O2-→as x andδincrease.For V→O2-migrations of the Sm0.0625Ce0.9375O1.9375 and Sm0.125Ce0.875O1.9375 systems,electrostatic attractions between Sm"and V,defect associations between Ce3 and V,and steric hindrances of Sm3+affect the migration energies.For O2→V migrations of the Sm0.125Ce0.875O1.875 and Sm0.25Ce0.75O1.875 systems,migration energies of O2-are affected by electrostatic repulsions between Sm3+and O2-and defect associations between Ce3+and V.Increases of the oxygen vacancy and Sm3+doping concentrations benefit the oxygen ion and vacancy migrations,respectively.展开更多
文摘使用GGA+U方法研究了Ca O或Ba O与Sm2O3共掺杂Ce O2体系几何和电子结构及氧离子迁移。计算结果表明,Ba和Sm均靠近氧空位时Ba Sm Ce30O63体系最稳定;Sm靠近,Ca远离氧空位时Ca Sm Ce30O63体系最稳定。Ba Sm Ce30O63和Ca Sm Ce30O63体系中均不存在Ce4+变价。对Ca Sm Ce30O63体系氧离子迁移的研究发现,当氧离子迁移到空位时,迁移能大小顺序为Em(3→V)<Em(1→V)<Em(4→V)<Em(2→V),这一规律源于氧离子与低价掺杂离子产生负电势之间的排斥作用;对Ba Sm Ce30O63体系氧离子迁移的研究发现,当空位迁移到周围氧离子时,迁移能大小顺序为Em(V→3)<Em(V→5)<Em(V→1),这一规律源于氧空位产生的正电势与低价掺杂离子产生的负电势之间的吸引作用。此外,Ca Sm Ce30O63体系最小迁移能小于Sm Ce31O63体系,证实了Ce O2-Sm2O3-Ca O体系离子电导率大于Ce O2-Sm2O3体系的实验结果。
基金Supported by the National Natural Science Foundation of China(No.51474133)Inner Mongolia Natural Science Foundation(No.2016MS0513)
文摘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)
文摘Influence of doping and oxygen vacancy concentrations on oxygen ion or oxygen vacancy(V)migration energies of SmxCe1-xO2-δ(x=0.0625,0.125,0.25 andδ=0.0625,0.125)systems using a GGA+U method are studied.Calculated results show that advantage migration types change from V→O2-to O2-→as x andδincrease.For V→O2-migrations of the Sm0.0625Ce0.9375O1.9375 and Sm0.125Ce0.875O1.9375 systems,electrostatic attractions between Sm"and V,defect associations between Ce3 and V,and steric hindrances of Sm3+affect the migration energies.For O2→V migrations of the Sm0.125Ce0.875O1.875 and Sm0.25Ce0.75O1.875 systems,migration energies of O2-are affected by electrostatic repulsions between Sm3+and O2-and defect associations between Ce3+and V.Increases of the oxygen vacancy and Sm3+doping concentrations benefit the oxygen ion and vacancy migrations,respectively.
