MgB_2(001)面超导结构的电子浓度第一原理分析

采用密度范函理论计算了金属化合物MgB2(001)薄膜结构的电子能带结构和状态密度,计算的交换相关能分别采用LDA和GGA。规范保守赝势的计算结果表明,晶格常数与实验值误差在很小的范围内,分析了引起MgB2(001)面结构超导转变时电子浓度和偏态密度的变化情况,发现构成该超导体结构的成键有三种,着重从结构的电子浓度变化分析了其超导特性,六角蜂窝状结构中硼原子间相互作用为sp2杂化的共价键,镁原子和硼原子之间是离子键结合,镁原子层是金属键结合,镁原子的价电子部分转移到硼原子的pz轨道,部分电子为镁原子层共用。MgB2的超导机制为强烈的电子-声子耦合,为B原子间强烈的共价作用形成,是传统S波超导体。对Mg元素同一主族的其它硼化物进行布居分析,发现MgB2中Mg原子电子转移明显强于BeB2和CaB2,说明电子浓度是引起超导转变的一个重要因素。

Principles study on band structure and DOS of MgB2(001)

Both GGA and LDA are applied to calculate the band structure and DOS of MgB2(001),the ionic "core" is represented by Pseudo potential.Crystal constants are in close with other experiment results.Three kinds of chemical bonds exist among Mg and B atoms,between magnesium and boride is ionic bond and metallic bond is the predominant interaction in the layer formed by magnesium atoms.A strong covalent bond in the form of sp2 hybrid between boride atoms is the most important factor which could affect the transition temperature of MgB2.Population analysis clearly shows that electrons are transferred from Mg to B,as a result,phonon-electron coupling in the layer of B is very strong.We also clarified the electron populations of BeB2 and CaB2 and compared the results among them,the electron transfer between metallic atom and B is mostly obvious in MgB2.