title: Molecular spin on surface: From strong correlation to dispersion interactions.
abstract: 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 optimal U 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 ΔEHLis 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 ΔEHLat large molecule-surface distances. Besides, we find that ΔEHLis decreased by the molecule-metal contact, which is shown to weaken the local ligand field around the magnetic center.
authors: Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang 550018, China.
authors: Yachao
authors: Y
authors: Zhang