Ca_3Co_4O_9及其掺Zn体系的电子结构

Electric Structure Calculation of Ca_3Co_4O_9 and Zn-doped Ones

用离散变分密度泛函方法(DFT-DVM)计算了Ca3Co4O9及其掺Zn体系的电子态密度,讨论了电子结构、化学键等与热电性能之间的关系。研究结果显示,价带和导带主要由Co3d,Zn3d和O2p原子轨道贡献,价带和导带之间的能隙宽度表现出半导体电子结构特征。掺Zn体系的能隙比不掺Zn的窄,掺Zn体系的共价键和离子键都比不掺Zn的弱。

The density of states （DOS） of Ca3Co4O9 and Zn-doped ones are calculated by using density functional and discrete variation method（DFT-DVM）. The relation between electronic structure, chemical bond and thermoelectric property is discussed. The research indicates that the highest valence band （HVB） and the lowest conduction band （LCB） are mainly contributed from Co3d, Zn3d and O2p atomic orbits. The property of semiconductor is shown from the gap between HVB and LCB. The gap of Zn-doped ones is less than that of Ca3Co4O9. The covalent and ionic bonds of Zn-doped ones are both weaker than those of Ca3Co4O9. The results imply that the thermoelectric property may be enhanced by adding Zn element into the system of Ca3Co4O9, which has been proved true.