Molecular spin on surface: From strong correlation to dispersion interactions
Molecular spin on surface: From strong correlation to dispersion interactions
复制标题
表面分子自旋：从强相关性到色散相互作用
DOI：
10.1063/1.4963338
复制
发表时间：
2016
影响因子：
4.4
通讯作者：
Zhang Yachao
中科院分区：
文献类型：
--
作者：
Zhang Yachao
几十年来，含3d/4f自旋载流子的表面支撑分子的磁性的可靠预测挑战了电子结构理论。在这里，我们解决这个问题与Hubbard-U校正的货车德瓦尔斯密度泛函（vdw-DF），纳入强相关效应的本地化电子和分散的相互作用参与的分子表面结合。通过对一系列具有不同配体场强的Fe（II）化合物的自旋态能量学进行拟合，我们发现vdW-DF的最佳U值远小于局域密度近似（LDA）的最佳U值，而与广义梯度近似（GGA）的最佳U值非常相似。我们发现，虽然vdW-DF+U高估了很大程度上的金属配位体的键距，预测的绝热高自旋低自旋能量分裂EHL是只有轻微的变化，相对于使用LDA+U的几何形状与实验一致。然后，我们使用Cu（111）负载的茂金属（M（C5 H5）2，M = Fe，和Co）作为原型例子来探索分子-表面相互作用的影响。我们发现，非本地色散相互作用，LDA和GGA描述不佳，而合理捕获的vdw-DF，是关键的再现在大分子表面距离的非局域EHL。此外，我们还发现分子与金属的接触削弱了磁性中心附近的局部配位场，从而降低了磁弹性流体动力学。
A reliable prediction of magnetic properties of surface-supported molecules containing 3d/4f spin carriers has challenged the electronic structure theory for decades. Here we tackle this problem with Hubbard-U corrected van der Waals density functional (vdW-DF), incorporating strong correlation effects of the localized electrons and dispersion interactions involved in the molecule-surface binding. By fitting the spin state energetics of a series of Fe(II) compounds with varying ligand field strength, we find that the optimalU value for vdW-DF is much smaller than that for the local density approximation (LDA) while quite similar to that for the generalized gradient approximation (GGA). We show that although vdW-DF+U overestimates largely the metal-ligand bond distance, the predicted adiabatic high-spin-low-spin energy splitting ∆EHL is only slightly changed with respect to that obtained using the LDA+U geometries consistent with experiment. Then we use Cu(111)-supported metallocene (M(C5H5)2, M = Fe, and Co) as a prototype example to explore the effects of the molecule-surface interactions. We show that the non-local dispersion interactions, poorly described by LDA and GGA while reasonably captured by vdW-DF, are critical for reproducing ∆EHL at large molecule-surface distances. Besides, we find that ∆EHL is decreased by the molecule-metal contact, which is shown to weaken the local ligand field around the magnetic center.