掺杂半导体β-FeSi_2电子结构及几何结构第一性原理研究

A first-principle study of electronic and geometrical structures of semiconducting β-FeSi_2 with doping

采用基于第一性原理的密度泛函理论全势线性缀加平面波法,使用广义梯度近似处理交换相关势能,首先计算了β-FeSi2的电子结构及其各元素各亚层电子的能态密度,β-FeSi2的电子能态密度主要由Fe的d层电子和Si的p层电子的能态密度确定;其次通过计算不同掺杂系统的总能量确定了掺杂原子在β-FeSi2中的置换位置,在β-FeSi2中,Co置换FeⅡ位置的Fe原子,Al置换SiⅠ位置的Si原子,这种择位置换与现有的计算结果完全一致;最后计算了Fe1-xCoxSi2和Fe(Si1-xAlx)2的电子结构,对它们的电子结构特征进行了分析,并探讨了电子结构对其热电性能(塞贝克系数、电传输及热传输性能)的影响.

Firstly, the electronic structure of β-FeSi2 and the density of states （DOS） of subshells of Fe and Si were calculated. The calculations were carried out using the self-consistent full-potential linearized augmented plane wave method within the density functional theory. The general gradient approximation was used to treat the exchange and correlation potential. The DOS of β-FeSi2 is mainly composed of d-shell electrons of Fe and p-shell electrons of Si. Secondly, the stable atomic substitution positions of doping atoms were determined by calculating the total energies for Fe1-xCoxSi2 and Fe（Si1-xAlx）2. The Fe atom at the FeⅡ position and the Si atom at the SiⅠ position were preferentially substituted by Co and Al, respectively. This preferential substitution is in good agreement with results of the existing publications. Finally, the elctronic structures of Fe1-xCoxSi2 and Fe（Si1-xAlx）2 were calculated and analyzed as well. The intrinsic relations between electronic structures of Fe1-xCoxSi2 and Fe（Si1-xAlx）2 and their respective thermoelectric properties including Seebeck coefficient, electric conductivity and thermal conductivity were discussed in detail.