CaX (X=S, Se, Te)带隙的GW近似修正

Band gaps of CaX (X=S, Se, Te) in GW approximation correction

摘要:

采用基于第一性原理下的局域密度近似(LDA)方法对岩石矿物结构Ca硫族化合物CaX (X=S, Se, Te)的晶格常数和电子结构进行了研究. 研究结果表明, 使用LDA方法得到的晶格常数与实验值符合得很好, 但带隙值却远低于实验值. 为了获得可靠的带隙值, 使用了GW(G格林函数, W库伦屏蔽相互作用)近似方法对Ca硫族化合物的带隙进行修正. 利用GW近似方法计算CaS 和CaSe的带隙值比利用LDA计算的带隙值高, 并且与实验值相吻合. 同时也预测了CaTe的带隙值, 尽管没有实验值作为参考, 但GW近似计算的结果应该是合适的值.

Abstract:

The structures and electronic properties of calcium chalcogenides CaX (X=S, Se, Te) in NaCl structure have been investigated by using the first-principle pseudopotential method based on density function theory within a LDA (local density approximation). The calculated lattice parameters are in excellent agreement with the experimental results, whereas the minimum gaps are much lower than the experimental ones. To get the reliable band gap values, we employ the GW (G is Green’s function and W is the screened Coulomb interaction) approximation method to correct the band gap values. The band gap values of CaS and CaSe using GW approximation have been improved compared to the obtained results from the LDA, which are in agreement with the experimental data. And we also predict the band gap value of the CaTe. It is expected that GW approximation should be very appropriate, though there is no experimental result for CaTe.