氢模型系统

本研究引入了一套包含四个氢模型系统的基准集，分别是一维链、一维环、二维三角格和三维紧密堆积金字塔。这些模型系统代表了不同维度和电子结构，用于探索和测试经典电子结构方法在强相关性条件下的效率。每个模型都考虑了氢-氢距离对相关性强度的影响，以及不同分子轨道基的使用（分散/局域）。通过计算各种相关性度量，包括二体累积量的范数、总量子信息和自旋-自旋相关函数，来表征这些模型。此外，为了研究系统大小对压缩效率的影响，还考虑了四个模型的H12、H14和H16类似物。这些模型对于评估多参考电子相关性处理中的计算方法性能特别重要，尤其是在仅应用于价轨道时。

This study introduces a benchmark set of four hydrogen model systems, namely one-dimensional chains, one-dimensional rings, two-dimensional triangular lattices, and three-dimensional close-packed pyramids. These model systems cover distinct dimensionalities and electronic structures, and are used to explore and test the efficiency of classical electronic structure methods under strong correlation conditions. For each model, the influence of hydrogen-hydrogen distance on correlation strength, as well as the employment of different molecular orbital bases (delocalized/localized), is considered. These models are characterized by calculating various correlation metrics, including the norm of two-body cumulants, total quantum information, and spin-spin correlation functions. Additionally, to investigate the effect of system size on compression efficiency, H12, H14 and H16 analogs of the four models are also taken into account. These models are particularly important for evaluating the performance of computational methods in multi-reference electronic correlation treatments, especially when the methods are only applied to valence orbitals.