用DFT +U模拟血红素：迈向精确自旋态能量学的一步
Simulation of Heme using DFT+U: a step toward accurate spin-state energetics
摘要：
我们研究DFT+U方法作为一个可行的解决方案来描述低的状态的配位和未配位铁血红素复合物。除了它们在有机金属化学中的核心作用外，这些化合物还代表了LDA、GGA和常见的混合泛函未能再现实验磁分裂的典型情况。特别是，咪唑五配位血红素被所有通常的DFT口味错误地描述为三重态。在这项研究中，我们表明，一个U参数接近4 eV导致自旋跃迁和分子几何形状的定量协议与实验，DFT+U表示一个有吸引力的工具，在铁卟啉络合物的描述，在一个大大降低成本相比，相关的量子化学方法。从第一性原理获得的U参数的可能性进行了探索，通过自洽的线性响应制定。我们发现，这种方法，这被证明是成功的，在其他铁系统，在这种情况下，产生一些高估的最佳值的U。
英文摘要：
We investigate the DFT+U approach as a viable solution to describe the low-lying states of ligated and unligated iron heme complexes. Besides their central role in organometallic chemistry, these compounds represent a paradigmatic case where LDA, GGA, and common hybrid functionals fail to reproduce the experimental magnetic splittings. In particular, the imidazole pentacoordinated heme is incorrectly described as a triplet by all usual DFT flavors. In this study we show that a U parameter close to 4 eV leads to spin transitions and molecular geometries in quantitative agreement with experiments, and that DFT+U represents an appealing tool in the description of iron porphyrin complexes, at a much reduced cost compared to correlated quantum-chemistry methods. The possibility of obtaining the U parameter from first-principles is explored through a self-consistent linear-response formulation. We find that this approach, which proved to be successful in other iron systems, produces in this case some overestimation with respect to the optimal values of U.
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