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首页> 外文期刊>Computational Materials Science >Quantum size effects in Pb/Si(111) thin films from density functional calculations
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Quantum size effects in Pb/Si(111) thin films from density functional calculations

机译：从密度泛函计算看Pb / Si（111）薄膜的量子尺寸效应

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The Pb/Si(111) thin films were simulated within the density functional theory (DFT). The well-known Perdew–Burke–Ernzerhof (PBE) version of the generalized gradient approximation (GGA) and its recent nonempirical successor Wu–Cohen (WC) issue were used to estimate the exchange-correlation functional. Lattice parameters were calculated for bulk of the Pb and Si compounds to obtain more reliable lattice mismatch at the interface to be consistent with our used full-potential method of calculations. The WC-GGA result predicts the lattice constants of the Pb and Si compounds better than the GGA when compared with experiment. We have found that the spin–orbit coupling (SOC) does not significantly influence the results. Our finding is in agreement with the recent observation of the Rashba-type spin– orbit splitting of quantum well states in ultrathin Pb/Si(111) films. Our result shows, in agreement with experiment, that the top site (T1) is the most stable phase. A combination of tight r and feeble p bonds has been found at the interface, which results in a covalent Pb–Si bond. Our calculated electric field gradient (EFG) predicts quantum size effects (QSE) with respect to the number of deposited Pb layers on the Si substrate. The QSE prediction shows that the EFG dramatically drops on going from first to second layer. The EFG calculation shows that this system is not an ideal paradigm to freestanding films.
机译：在密度泛函理论（DFT）中模拟了Pb / Si（111）薄膜。著名的Perdew-Burke-Ernzerhof（PBE）版本的广义梯度近似（GGA）及其最近的非经验后继者Wu-Cohen（WC）问题被用来估计交换相关函数。计算了大部分Pb和Si化合物的晶格参数，以获得界面处更可靠的晶格失配，这与我们使用的全电势计算方法一致。与实验相比，WC-GGA结果比GGA更好地预测Pb和Si化合物的晶格常数。我们发现自旋轨道耦合（SOC）不会显着影响结果。我们的发现与最近在超薄Pb / Si（111）薄膜中量子阱态的Rashba型自旋轨道分裂的观察结果一致。我们的结果表明，与实验一致，顶部站点（T1）是最稳定的阶段。在界面处发现了紧密的r键和弱的p键的结合，这导致了共价的Pb-Si键。我们计算出的电场梯度（EFG）相对于在Si衬底上沉积的Pb层数预测了量子尺寸效应（QSE）。 QSE预测表明，从第一层到第二层，EFG急剧下降。 EFG计算表明，该系统不是独立电影的理想范例。

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