Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
J Chem Phys. 2012 Jul 14;137(2):024306. doi: 10.1063/1.4732123.
Photoabsorption spectra are calculated for the magic number clusters, (CdSe)(3) and (CdSe)(6), using an all-electron mixed basis GW scheme with the excitonic effect incorporated by solving the Bethe-Salpeter equation (BSE). The GW+BSE calculation provided clear size dependence of the optical gap as expected, while magnitude of the gap is overestimated compared to available experimental one. The gap is found very similarly overestimated when using the local density approximation (LDA) within the density functional theory because accidental error cancellation occurs between the significantly underestimated LDA gap and the excitonic effect neglected therein. The excitonic states are described by superposition of many one-particle states that would not be properly described within a one-particle theory, as clearly visualized in the plot of the exciton wavefunctions.
采用包含激子效应的全电子混合基 GW 方案，计算了幻数团 (CdSe)(3) 和 (CdSe)(6) 的光吸收谱。通过求解贝塞耳-薛定谔方程 (BSE)，计算中考虑了激子效应。GW+BSE 计算给出了预期的光学带隙的明显尺寸依赖性，而与可用的实验值相比，带隙的大小被高估了。当在密度泛函理论中使用局域密度近似 (LDA) 时，也会发现带隙被非常相似地高估，因为在那里显著低估的 LDA 带隙和被忽略的激子效应之间发生了偶然误差的抵消。激子态是由许多单粒子态的叠加描述的，在单粒子理论中不能得到正确的描述，这在激子波函数的图中可以清楚地看到。
