Identifying Practical DFT Functional for Predicting 0D and 1D Organic Metal Halide Hybrids

Low dimensional organic metal halide hybrids (LD-OMHHs) have recently emerged as a new class of functional materials with various potential applications in optical, magnetic, and quantum information technologies. The high-throughput discovery and understanding of these materials necessitate identifying the best theoretical methods for generating reliable predictions of properties compared to experimental results. One of the key properties that has been studied is the band gap. This work systematically benchmarks several widely used density functional theory (DFT) functionals as well as the impact of spin-orbit coupling on band gap predictions for 115 experimentally reported LD-OMHHs. Surprisingly, it was found that the band gap predicted by GGA aligns similarly or better with experimentally measured values compared with two meta-GGA methods. Moreover, the inclusion of spin-orbital coupling has limited influence on band gap prediction. Such behavior can be understood by the potential existence of large excitonic effects in LD-OMHHs, which deviate computed fundamental gap from high-level DFT theory from experimental optical bandgap. Our research also reveals that the utilization of GGA functional without spin orbital coupling can be a practical and efficient method for the high-throughput screening of LD-OMMHs with reasonable band gaps.