YBCO超导体中化学键与电子结构
来源期刊:中南大学学报(自然科学版)1990年第5期
论文作者:尹周澜 高孝恢 严辉 伍小玲
文章页码:551 - 553
关键词:超导体; 化学键; 电子结构/YBCO
Key words:superconductor; chemical bonds; electronic stuctures/YBCO
摘 要:本文用半经验CNDO/2量子化学计算方法,对YBCO的结构单元及晶胞作了计算,结果指出:1.采用簇模型不能较好地反映YBCO晶体性质。2.YBCO中Cu(2)的氧化态为(+2),Cu(1)的氧化态为(+1.5),Cu(1)也可能是在(+2)与(+1)两个氧化态之间共振。3.铜的电子组态分别为Cu(2)(dxy2dx22dyz2dx2-y21dz22),Cu(1)(dxy2dxz2]dyz2dx2-y22dz21)。这种组态是YBCO形成层状氧缺位结构的主要原因。4.超交换作用在YBCO中普遍存在,但铜-氧面间这种作用最大,超导电流在其间进行最为有利。5.Y,Ba在YBCO中的主要作用是促成Cu(dxy)与O(P)形成最高占领杂化带。
Abstract: Using semiempiric CNDO/2 method to calculate the structural units andcell of YBCO,the following results arc obtained:1.Cluster models can not show the real propcrtics of YBCO crystal well.2.The oxidation state of Cu(2)is(+2),while that of Cu(1)is(+1.5)and perhaps Cu(1)resonates between(+1)and(+2).3.The electronic configurations of Cu(2)and Cu(1)are dxy2dxz2dyz2 dx2-y21dz22and dxy2dxz2dyz2dx2-y22dz12 respectively.4.Generally,there exists superexchange effect in YBCO which is thc mosteffective between Cu-O planes,through which superconducting current flows.5.Y and Ba in YBCO help to bring about dxy orbitals of copper and porbitals of oxygen into the highest occupied hybrid band.