Despite its simplicity and relevance for the description of electronic correlations in solids, the Hubbard model is seldom inarguably realized in real materials. Here, we show that monolayer Nb₃Cl₈ is an ideal candidate to be described within a single-orbital Hubbard model, constructed within a “molecular” rather than atomic basis set using ab initio constrained random phase approximation calculations. We provide the necessary ingredients to connect experimental reality with ab initio material descriptions and correlated electron theory, which clarifies that monolayer Nb₃Cl₈ is a Mott insulator with a gap of about 1.4 to 2.0 eV depending on its dielectric environment. Comparisons to an atomistic three-orbital model show that the single-molecular-orbital description is adequate and reliable. We further comment on the electronic and magnetic structure of the compound and show that the Mott insulating state survives in the low-temperature bulk phases of the material featuring distinct experimentally verifiable characteristics.

尽管哈伯德模型简单且与描述固体中的电子相关性相关，但它很少在实际材料中无可争议地实现。在这里，我们表明单层 Nb ₃ Cl ₈是在单轨道哈伯德模型中描述的理想候选者，该模型使用从头开始约束随机相位近似计算在“分子”而不是原子基组内构建。我们提供了将实验现实与从头算材料描述和相关电子理论联系起来的必要成分，这阐明单层 Nb ₃ Cl ₈是莫特绝缘体，其带隙约为 1.4 至 2.0 eV，具体取决于其介电环境。与原子三轨道模型的比较表明，单分子轨道描述是充分且可靠的。我们进一步评论了该化合物的电子和磁性结构，并表明莫特绝缘态存在于该材料的低温体相中，具有独特的可实验验证的特性。