中文摘要：

基于密度泛函理论（DFT）在广义梯度（GGA）下计算了钴磷族化合物BaT2P2和BaT2As2（T=Co,Rh,Ir）的电子结构.研究发现在BaCo2P2和BaCo2As2中,由于范霍夫畸点位于费米面附近使得费米能级处的态密度非常高,从而导致由斯通纳机理引起的巡游铁磁不稳定性.在从Co到Rh然后到Ir的化合物中由于d轨道的空间扩展性增强,直接的d-d以及d-p杂化都会增强,这使得形成范霍夫畸点的d-d：σ键的反键态被推往远离费米能级之上更高的能量区间,从而使得在费米面处的态密度下降,斯通纳机理消失,从而使得Rh和Ir的化合物都稳定在非磁态.本文仔细研究并比较了这些化合物间的电子结构及其演化,计算表明自旋-轨道耦合相互作用对电子结构影响很小.

英文摘要：

We study the electronic structure of cobalt pnictides：BaT2P2 and BaT2As2（T=Co,Rh,Ir） by the density functional theory within generalized gradient approximation,and find that the ferromagnetisms in BaCo2As2 and BaCo2P2 are due mostly to the high density of states（Van-Hove singularity） at Fermi level,which induce Stoner ferromagnetism.In these compounds,from Co-3d to Rh-4d,then to Ir-5d,the d-d bonding and the d-p bonding in the TX4（X=P,As） layers are strengthened.As a result,the antibonding d-d states are pushed away from the Fermi level,and the ferromagnetisms are suppressed in Rh and Ir compounds.The evolutions and the detailed electronic structures of these compounds are studied and compared,and spin orbital coupling interaction is negligible.