采用基于密度泛函理论框架下的第一性原理平面波超软赝势法,对不同As掺杂浓度FeS 2的几何结构、电子结构和光学性质进行计算和讨论.采用2×2×2(Fe32S63As),2×2×1(Fe16S31As)和2×1×1(Fe8S15As)的超晶胞模型,用1个As原子取代1个S原子,使掺杂浓度分别为1.93%、3.82%和7.48%(质量分数),然后进行3种掺杂体系的计算,并将其与理想体系进行对比.几何结构与电子结构的计算结果表明:As掺杂使得FeS 2的晶格常数和晶胞体积增大,导带部分下移,禁带宽度减小,并且在-10.4~-9.5 eV的浅部价带产生了由As的p态贡献的杂质能级.光学性质计算结果表明,掺杂后Fe(S 1-x As x)2的静态介电常数、折射率和光电导率在一定范围内均随着掺杂量的增大而明显增大,说明As掺杂显著增强了FeS 2对光的吸收以及光电转换效率.
Aimed at verifying the effect of As doping concentration on FeS2, geometrical structure, electronic structure and optical properties of As-doped FeS2 were calculated using pseudo-potential plane-wave method of the first principle based on the density function theory. Three supercells (2×2×2, 2×2×1 and 2×1×1) were introduced to achieve different doping concentrations (1.93%, 3.82% and 7.48%, mass fraction). The results of geometrical structure, electronic structure show that lattice constant and volume of unit cell increase with As addition, the conduction band moves negatively while the width of forbidden band decreases. Moreover, the density of states in the range of-10.4--9.5 eV exhibits impurity level composed of As p. The calculation of optical properties reveals the static dielectric constant, refractive index and photo conductivity aggrandize with the ever-increasing doping concentration, which indicates FeS2 doped As possesses stronger absorption capacity of light and higher photoelectric conversion efficiency. Therefore, the calculation lays some theory foundation for exploitation and development of FeS2 photoelectric materials.
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