Investigation of local distortion effects on X-ray absorption of ferroelectric perovskites from first principles simulations
Investigation of local distortion effects on X-ray absorption of ferroelectric perovskites from first principles simulations
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DOI：
10.1039/d2nr05732h
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发表时间：
2023-02-13
期刊：
影响因子：
6.7
通讯作者：
Pascal, Tod A.
中科院分区：
文献类型：
--
作者：
Abbasi, Pedram;Fenning, David P.;Pascal, Tod A.
了解铁电极化在调节晶体的电子和结构特性中的作用对于推进这些材料克服各种技术和科学挑战至关重要。然而，由于在执行实验方法与所需的分辨率，或在解释其中的方法的结果的困难，这些表面的纳米级形态和响应外部电场尚未得到适当的阐述。在这项工作中，我们调查的BaTiO 3钙钛矿铁电极化和局部扭曲的效果，使用两种广泛使用的计算方法，治疗多体性质的X射线激发使用不同的哲学，即多体，δ自洽场行列式（MB-Δ SCF）和Bethe-Salpeter方程（BSE）的方法。我们表明，与我们的实验相一致，这两种方法一致地预测较高的激发的主峰在O-K边缘的表面向上极化。然而，mb-Delta SCF方法大多未能捕获的L-2，L-3分离的Ti-L边缘，由于缺乏自旋轨道耦合的Kohn-Sham密度泛函理论（KS-DFT）在广义梯度近似水平。另一方面，最有前途的，我们表明，GW/BSE方法的应用成功地再现了实验XAS，无论是相对峰值强度，以及L-2，L-3分离在Ti-L边缘铁电开关。因此，模拟XAS被证明是一个强大的方法捕捉复杂材料的纳米结构，我们强调需要多体微扰方法，明确考虑核心孔和多重态效应，捕捉这些系统中的基本物理。
Understanding the role of ferroelectric polarization in modulating the electronic and structural properties of crystals is critical for advancing these materials for overcoming various technological and scientific challenges. However, due to difficulties in performing experimental methods with the required resolution, or in interpreting the results of methods therein, the nanoscale morphology and response of these surfaces to external electric fields has not been properly elaborated. In this work we investigate the effect of ferroelectric polarization and local distortions in a BaTiO3 perovskite, using two widely used computational approaches which treat the many-body nature of X-ray excitations using different philosophies, namely the many-body, delta-self-consistent-field determinant (mb-Delta SCF) and the Bethe-Salpeter equation (BSE) approaches. We show that in agreement with our experiments, both approaches consistently predict higher excitations of the main peak in the O-K edge for the surface with upward polarization. However, the mb-Delta SCF approach mostly fails to capture the L-2,L-3 separations at the Ti-L edge, due to the absence of spin-orbit coupling in Kohn-Sham density functional theory (KS-DFT) at the generalized gradient approximation level. On the other hand, and most promising, we show that application of the GW/BSE approach successfully reproduces the experimental XAS, both the relative peak intensities as well as the L-2,L-3 separations at the Ti-L edges upon ferroelectric switching. Thus simulated XAS is shown to be a powerful method for capturing the nanoscale structure of complex materials, and we underscore the need for many-body perturbation approaches, with explicit consideration of core-hole and multiplet effects, for capturing the essential physics in these systems.