块状ZnX（X = O，S，Se，Te），ZnF2和ZnO / ZnF2的结构和电子性质：PBE，PBE + U和混合HSE功能内的DFT研究。,The Journal of Physical Chemistry A

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块状ZnX（X = O，S，Se，Te），ZnF2和ZnO / ZnF2的结构和电子性质：PBE，PBE + U和混合HSE功能内的DFT研究。
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-05-04 , DOI: 10.1021/acs.jpca.9b11415
Efracio Mamani Flores _{1,

2} , Mário L Moreira ₁ , Maurício Jeomar Piotrowski ₁

Affiliation

在这里，我们研究了本体ZnX（X = O，S，Se，Te）和ZnF2系统的晶体结构，这是了解ZnX和ZnO / ZnF2界面等基于Zn的系统的结构的第一步。对于可能的技术应用的重要性。此外，基于密度泛函理论（DFT）计算的充分方法学描述是必要的。众所周知，基于局部或半局部交换相关函数的普通DFT计算无法为这些系统描述正确的带隙能量，而诸如基于混合函数的非局部方法可以补偿带隙的低估。为了促进评估，在半本地Perdew-Burke-Ernzerhof（PBE）和两个非本地功能中进行了DFT研究，Heyd-Scuseria-Ernzerhof（HSE）和PBE + U功能的混合体。我们的结果证实，与实验值相比，PBE低估了ZnX化合物的能带隙值，从33.0到42.8％。应用混合HSE泛函，我们获得了与非局部精确交换的分离范围有关的带隙依赖性，通常可以减小带隙误差并改善晶格常数描述。另外，使用PBE + U方法，我们研究了Zn d态的定位及其对ZnX和ZnF2中带隙的影响。我们发现带隙随着Hubbard参数的增加而增加，这引入了针对Zn 3d态的现场库仑校正。在相同的上下文中，突出显示了包括O 2p状态（和X p状态）的Hubbard校正的相关性。从而，考虑到PBE + U，相对于实验值，例如ZnO带隙的误差降低到5.1％。最后，发现ZnO-12L / ZnF2-4L超晶格表现出常规的电子特性，例如低的基带隙，小于任何一种母体材料。我们的第一性原理计算表明，带电层的意外减小是由导电层引起的，这些导电层倾向于穿透界面并减小带隙，从而导致载流子通过界面传输到ZnF2，即使带隙较大对于电荷转移，对于光伏应用可能是有趣的。例如低的基带隙，小于任何一种母体材料。我们的第一性原理计算表明，带隙的意外减少是由倾向于穿透界面并减小带隙的导电层引起的，从而导致载流子通过界面传输到ZnF2，即使带隙较大对于电荷转移，对于光伏应用可能是有趣的。例如低的基带隙，小于任何一种母体材料。我们的第一性原理计算表明，带隙的意外减少是由倾向于穿透界面并减小带隙的导电层引起的，从而导致载流子通过界面传输到ZnF2，即使带隙较大对于电荷转移，对于光伏应用可能是有趣的。

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Structural and Electronic Properties of Bulk ZnX (X = O, S, Se, Te), ZnF2, and ZnO/ZnF2: A DFT Investigation within PBE, PBE + U, and Hybrid HSE Functionals.

Here, we have studied the crystalline structure of bulk ZnX (X = O, S, Se, Te) and ZnF2 systems as a first step to understand the structures like ZnX and Zn-based systems like ZnO/ZnF2 interfaces, which are of utmost importance for possible technological applications. In addition, an adequate methodological description based on density functional theory (DFT) calculations is necessary. It is well known that plain DFT calculations based on local or semilocal exchange-correlation functionals fail to describe the correct band gap energy for these systems, whereas nonlocal approaches, such as hybrid-based functionals, can compensate the underestimation of band gap. To contribute to the assessment, DFT studies were performed within semilocal Perdew-Burke-Ernzerhof (PBE) and two nonlocal functionals, hybrid Heyd-Scuseria-Ernzerhof (HSE) and PBE + U functionals. Our results confirm that PBE underestimates the energy band gap values, from 33.0 to 42.8% for ZnX compounds compared to the experimental values. Applying the hybrid HSE functional, we obtained a band gap dependency in relation to the range of separation of the nonlocal exact exchange, in general decreasing the band gap error and improving the lattice constant description. In addition, using the PBE + U approach, we have investigated the localization of the Zn d-states and its effect on the band gap in ZnX and ZnF2. We found an increase in the band gap with increasing Hubbard parameter, which introduces on-site Coulomb corrections for the Zn 3d states. In the same context, the relevance to include the Hubbard corrections for the O 2p states (and X p states) is highlighted. Thus, considering PBE + U, the error in ZnO band gap, for example, decreases to 5.1%, in relation to the experimental value. Finally, ZnO-12L/ZnF2-4L superlattices are found to exhibit conventional electronic properties, such as low fundamental band gap, smaller than either of the parent materials. Our first-principles calculations reveal that the unexpected band gap reduction is induced by the conducting layers that tend to penetrate the interface and decrease the band gap, leading to the transport of carriers through the interface to ZnF2, which, even with a high band gap for charge transfer, can be interesting for photovoltaic applications.

更新日期：2020-04-24

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