理论分析Ca位掺杂对Ca_3Co_2O_6电子结构的影响

Theoretical Analysis on Electronic Structure of Ca-for-Sr Substitution in Ca_3Co_2O_6

通过建立原子簇模型,运用密度泛函离散变分法讨论了Ca3Co2O6及掺Sr体系的电子结构与化学键。掺Sr前后价带和导带之间的能隙宽度表现出半导体特征,且掺Sr后能隙变窄,价带和导带主要由Co3d和O2p轨道贡献,表明一维Co-O链在电学性能方面起主导作用。通过对化学键分析可知,掺Sr后有利于降低Co-O链的键性。由此可知,掺Sr有利于改善Ca3Co2O6的热电性能。

Building the atom-cluster models, the electronic structure and chemical bonds of Ca3 Co2 O6 and Ca- for-St substitution were calculated by density function and discrete variation method（DFT-DVM）, The semiconductor properties of these two systems were shown from the gap between the highest valence band（HVB） and the lowest conduction（LCB）. Furthermore, the gap of Sr-doped one was less than that of Ca3 Co2 O6. The HVB and LCB were mainly contributed from C03d and O2p atomic orbitals, which indicated obviously that 1D Co-O chains play an important role in electric property of Ca3 Co2 O6 and doped system. It can be concluded that chemical bonds of Co-O chains in Srdoped are weaker than those of Ca3 Co2 O6 from comparing covalent bond orders and atomic net charges. Thus thermo- electric properties may be improved from Ca-for-Sr substitution in Ca3 Co2 O8.