Accurate and efficient band-gap predictions for metal halide perovskites at finite temperature: corresponding atomic structures at the certain temperature

We develop a computationally efficient scheme to accurately determine finite-temperature band gaps. We here focus on materials belonging to the class ABX3 (A = Rb, Cs; B = Ge, Sn, Pb; and X = F, Cl, Br, I), which includes halide perovskites. First, an initial estimate of the band gap is provided for the ideal crystalline structure through the use of a range-separated hybrid functional, in which the parameters are determined nonempirically from the electron density and the high-frequency dielectric constant. Next, we consider two kinds of band-gap corrections to account for spin-orbit coupling and thermal vibrations including zero-point motions. In particular, the latter effect is accounted for through the special displacement method, which consists in using a single distorted configuration obtained from the vibrational frequencies and eigenmodes, thereby avoiding lengthy molecular dynamics. The sequential consideration of both corrections systematically improves the band gaps, reaching a mean absolute error of 0.17 eV with respect to experimental values. The computational efficiency of our scheme stems from the fact that only a single calculation at the hybrid-functional level is required and that it is sufficient to evaluate the corrections at the semilocal level of theory. Our scheme is particularly convenient for large-size systems and for the screening of large databases of materials. This entry provides the ideal atomic structures and the distorted atomic structures at certain temperature including zero-point motions, generated by special displacement method.

本工作提出了一种计算高效的方案，可精准确定有限温度下的能带隙。本研究聚焦于ABX₃型材料（其中A为Rb、Cs；B为Ge、Sn、Pb；X为F、Cl、Br、I），该类材料涵盖卤化物钙钛矿。首先，针对理想晶体结构，我们通过范围分离杂化泛函（range-separated hybrid functional）给出能带隙的初始估算值，该泛函的参数可通过电子密度与高频介电常数非经验地确定。随后，我们引入两类能带隙修正项，以分别考虑自旋轨道耦合（spin-orbit coupling）与包含零点振动在内的热振动效应。具体而言，热振动效应可通过特殊位移法（special displacement method）进行处理：该方法仅需利用由振动频率与本征模得到的单个畸变构型，从而避免了耗时的分子动力学模拟。通过依次应用这两类修正，能带隙的计算精度得到系统性提升，与实验值相比的平均绝对误差仅为0.17 eV。本方案的计算高效性源于两点：仅需完成一次杂化泛函层级的计算，且修正项的评估仅需在半局域理论层级下进行即可。该方案尤其适用于大尺寸体系以及大规模材料数据库的筛选工作。本数据集条目包含通过特殊位移法生成的理想原子构型，以及包含零点振动在内的特定温度下的畸变原子构型。