钙钛矿型YNiO_3电子能带结构的第一性原理

First-principles of Electronic Band Structure in YNiO_3 Perovskite

采用第一性原理计算了钙钛矿材料YNiO3正交相、单斜相的电子能带结构。计算结果表明:YNiO3正交相为直接带隙,带隙大小约为0.99 eV;单斜相低能导带向费米面移动进入带隙区,与费米面相交而部分填满,使其具有金属性而导电。同时发现,Ni在正交相中只存在一种组态Ni3+,而在单斜相中则存在Ni2+和Ni4+两种不同的组态,即存在电荷歧化2Ni3+→Ni2++Ni4+。

The electronic band structures of both the orthorhombic and monoclinic YNiO3 were calculated by using the first-principles method within the generalized gradient approximation.The calculated results show that the band gap for the monoclinic is the direct band-gap,corresponding to the values about 0.99 eV.The orthorhombic phase is metallic phase by the conduction band shift to the Fermi face.A comparison of the electron-density map between orthorhombic and monoclinic structures indicates that there are different types of charge ordering found in the two systems.In the orthorhombic phase,all nickel ions are trivalent.In the monoclinic phase,charge disproportionation occurs,that is,2 Ni3+→Ni2++ Ni4+.