采用基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,结合局域自旋密度近似和 Hubbard U 修正,对不同Co离子自旋态下及Ga掺杂LaCoO3的超晶胞体系进行了几何结构优化,计算并分析了它们的电子结构。结果表明,当Co离子处于低自旋态时,LaCo O 3为非磁绝缘性的绝缘体；当 Co 离子被激发到中间自旋态时,由于强烈的p-d轨道杂化作用,LaCo O 3转变成一个有磁性的半金属体；当Co离子处于高自旋态时,体系呈现金属铁磁性,磁矩由中间自旋态的0．91μB 增大到高自旋态的2．2μB。Ga掺杂后,体系的Co3d态电子和 Ga4p态电子以及 O2p 态电子在费米能级附近发生p-d轨道杂化,引入杂质带,形成受主能级,使体系的导电能力增强,体系呈现半金属铁磁性,其净磁矩为4．01μB。
The geometrical structures of LaCoO3 with different Co3+ spin states and Ga doping were optimized by using the first principle density functional theory based on the full potential linearized augumented plane wave method and combined with local density approximation plus Hubbard U (LSDA+U).The electronic structures were calculated and discussed in details.LaCoO3 is a non-magnetic insulator when Co3+ is low spin state (LS). The strong hybridization of Co3d and O2p electrons makes LaCoO3 becomes a magnetic half metal when Co3+translate to intermediate spin state (HS).It shows metallic ferromagnetic when Co3+ is high spin state (HS). The magnetic moments increase form 0.91 of IS to 2.2μB of HS.Ga doping makes Co3d electrons hybrid with Ga4p and O2p electrons,introduces the impurity bands to form acceptor energy level.The system enhances its conductivity and shows half metallic ferromagnetic.Its net magnetic moment is 4.01μB.
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