基于全电子方法和TB-mBJ势的硫化镉多型体能带结构计算

First-principles Study of Cadmium Sulfide Polymorphs with All-electron Method and TB-mBJ Potential

常见的硫化镉多型体为纤锌矿结构硫化镉(w-CdS)和闪锌矿结构硫化镉(zb-CdS).在高压下w-CdS或zb-CdS都会向岩盐矿结构(rs-CdS)转变.在有外加压强条件下的CdS电子能带结构在实验上一直备受关注.全势线性缀加平面波方法计算所得电子能带结构表明:w-CdS与zb-CdS具有直接带隙,rs-CdS是间接带隙材料.为了更准确的预测禁带宽度,我们探讨了Hubbard U修正和TB-mBJ势的作用,采用TB-mBJ势的能带结构计算得到的w-CdS和zb-CdS的禁带宽度分别为2.74eV和2.66eV,和实验值比较接近.我们采用TB-mBJ势对不同外压下的rs-CdS进行了能带结构计算,指出rs-CdS在高压下仍然保持价带顶在L点,导带底在X点的间接带隙特征.分析了禁带宽度随压强增大而减小的趋势,采用TB-mBJ势的结果和rs-CdS高压下的光学实验结果符合.

Frequently observed and synthesized cadmium sulfide polymorphs have wurtzite structure or zinc blende structure.Both wurtzite CdS(w-CdS)and zincblende CdS(zb-CdS)will transform into rock salt structure(rs-CdS)under high pressure.The band structure of CdS under high pressure is always an attractive issue for research.The band structure calculations using the full potential linearized augmented plane wave method show that w-CdS and zb-Cds have direct band gap,and rs-CdS is an indirect band gap semiconductor.In order to predict the band gap more accurately,we discuss the effect of Hubbard U correction and TB-mBJ potential.The band gap of the w-CdS and the zb-CdS calculated by TB-mBJ potential are 2.74eV and 2.66eV,respectively,which are close to the experimental values.We use the TB-mBJ potential to calculate the electronic band structure of rs-CdS under different pressures.It is indicated that rs-CdS still maintains the indirect band gap character with the valence band maximum located at the L point and the conduction band minimum at the X point under high pressure.The band gap decreases with the pressure increasing.The band gaps predicated by the DFT calculation with TB-mBJ potential are consistent with the experimental absorption measurements for high pressure rs-CdS.