Cu3O1217-模型簇的电子态

在铜氧基超导体中,超导电性与接近充满的Cu3d-O2p价带空穴浓度有关.若干研究表明,添加空穴进入CuO_2面σ(P_(x,y))轨道,但另外一些工作认为,空穴态存在于Cu-O面π(p_(x,y))或π(p_z)轨道,还有其它一些作者建议,空穴集居于BaO面上σ(p_z)轨道.通过理论计算来区分未占O2p态的特征具有重要意义.因此,本文对模型簇Cu_3O_(12)~(17-)进行了Fenske-Hall MO计算,探讨了添加空穴态的对称性和添加对Cu-O键强度的影响.

ELECTRONIC STATES OF THE Cu3O1217- MODEL CLUSTER

The Fenske-Hall molecular orbital calculations were performed on the model cluster Cu_3O_(12)~(17-). The calculated results revealed that the valence levels are mainly composed of Cu d and O p components, and the levels near E_f are predominately of O p nature. Oxidation removes the antibonding electrons from the Cu (1) d_(z~2-y~2) MO and strengthens the chain Cu(1)—O(1) and Cu(1)—O(4) bonds so that they have slightly larger overlap population than the plane Cu(2)—O(2) and Cu(2)—O(3) bonds. The oxidation beyond the Cu~(2+) state does not lead to Cu~(3+) but to O~- state so that the O(1) as well as O(4) ions have slightly smaller electron charge than the O(2) and O(3) ions. The holes introduced by doping reside primarily on the Cu—O chain with dominantly sigma O(4) 2p_z character.