卤化物钙钛矿哈伯德模型中的在位和位间电子关联
Onsite and intersite electronic correlations in the Hubbard model for halide perovskites
摘要：
卤化物钙钛矿（HPs）由于其在可见光范围内具有良好的禁带宽度而被广泛认为是一种很有前途的光伏和发光材料。采用（半）局部交换相关泛函的密度泛函理论（DFT）计算通常低估了这些系统的带隙。要准确描述HP的电子结构，通常需要更高阶的理论，例如Heyd-Scuseria-Ernzerhof（HSE）混合密度泛函和GW近似，这些近似比标准DFT计算昂贵得多。在这里，我们研究了三种代表性类型的HP，ABX 3卤化物钙钛矿，空位有序双钙钛矿（VODP），和键合的卤化物钙钛矿（BDHPs），使用DFT+U+V与现场U和intersite V Hubbard参数计算自洽没有先验假设。包括哈伯德校正提高了所有三种类型的HP的带隙预测精度的先进方法的类似水平。此外，自洽的Hubbard U是一个有意义的指标，在HP中的多价金属原子的真实局部电荷状态。包含的intersite Hubbard V是至关重要的，以适当地捕获在BDHPs，具有卤素八面体的呼吸模式失真的相邻原子上的价电子之间的杂化。特别是，哈伯德参数和晶体几何形状的同时收敛使得BDHPs的带隙预测精度优于HSE，但成本仅为一小部分。我们的工作突出了使用自洽的Huabbard参数时，往往具有复杂的竞争现场本地化和站点间杂交处理HP的重要性。
英文摘要：
Halide perovskites (HPs) are widely viewed as promising photovoltaic and light-emitting materials for their suitable band gaps in the visible spectrum. Density functional theory (DFT) calculations employing (semi)local exchange-correlation functionals usually underestimate the band gaps for these systems. Accurate descriptions of the electronic structures of HPs often demand higher-order levels of theory such as the Heyd-Scuseria-Ernzerhof (HSE) hybrid density functional and GW approximations that are much more computationally expensive than standard DFT. Here, we investigate three representative types of HPs, ABX3 halide perovskites, vacancy-ordered double perovskites (VODPs), and bond disproportionated halide perovskites (BDHPs), using DFT+U+V with onsite U and intersite V Hubbard parameters computed self-consistently without a priori assumption. The inclusion of Hubbard corrections improves the band gap prediction accuracy for all three types of HPs to a similar level of advanced methods. Moreover, the self-consistent Hubbard U is a meaningful indicator of the true local charge state of multivalence metal atoms in HPs. The inclusion of the intersite Hubbard V is crucial to properly capture the hybridization between valence electrons on neighboring atoms in BDHPs that have breathing-mode distortions of halide octahedra. In particular, the simultaneous convergence of both Hubbard parameters and crystal geometry enables a band gap prediction accuracy superior to HSE for BDHPs but at a fraction of the cost. Our work highlights the importance of using self-consistent Huabbard parameters when dealing with HPs that often possess intricate competitions between onsite localization and intersite hybridization.
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