School of Information Science, JAIST, Nomi, Ishikawa, Japan.
National Institute of Materials Science, Tsukuba, Ibaraki, Japan.
Sci Rep. 2017 May 17;7(1):2011. doi: 10.1038/s41598-017-01668-6.
We have applied DMC to evaluate relative stability of the possible electronic configurations of an isolated FePc under D symmetry, considering some fixed nodes generated from different methods. They predict A ground state consistently, supporting preceding DFT studies, with confidence overcoming the ambiguity about exchange-correlation (XC) functionals. By comparing DMC with several XC, we clarified the importance of the short-range exchange to describe the relative stability. We examined why the predicted A is excluded from possible ground states in the recent ligand field based model. Simplified assumptions made in the superposition model are identified to give unreasonably less energy gain for A when compared with the reality. The state is found to have possible reasons for the stabilization, reducing the occupations from an unstable anti-bonding orbital, avoiding double occupation of a spatially localized orbital, and gaining exchange energy by putting a triplet spin pair in degenerate orbitals.
我们已经应用 DMC 来评估在 D 对称性下，孤立的 FePc 可能的电子构型的相对稳定性，同时考虑了来自不同方法的一些固定节点。它们一致地预测 A 基态，支持之前的 DFT 研究，克服了关于交换相关（XC）泛函的模糊性。通过比较 DMC 和几种 XC，我们阐明了短程交换对描述相对稳定性的重要性。我们研究了为什么最近基于配体场的模型预测的 A 被排除在可能的基态之外。通过与实际情况进行比较，确定了超叠加模型中简化假设的不合理性，使得 A 的能量增益大大降低。发现该状态具有稳定化的可能原因，通过从不稳定的反键轨道中减少占据，避免空间局域轨道的双重占据，以及通过将三重态自旋对放入简并轨道中获得交换能。
