The disclosure of mesoscale behaviour of a 3d-SMM monolayer on Au(111) through a multilevel approach

Here we present a computational study of a full- and a half-monolayer of a Fe4 single molecule magnet ([Fe4(L)2(dpm)6], where H3L = 2-hydroxymethyl-2-phenylpropane-1,3-diol and Hdpm = dipivaloyl-methane, Fe4Ph) on an unreconstructed surface of Au(111). This has been possible through the application of an integrated approach, which allows the explicit inclusion of the packing effects in the classical dynamics to be used in a second step in periodic and non-periodic high level DFT calculations. In this way we can obtain access to mesoscale geometrical data and verify how they can influence the magnetic properties of interest of the single Fe4 molecule. The proposed approach allows to overcome the ab initio state-of-the-art approaches used to study Single Molecule Magnets (SMMs), which are based on the study of one single adsorbed molecule and cannot represent effects on the scale of a monolayer. Indeed, we show here that it is possible to go beyond the computational limitations inherent to the use, for such complex systems, of accurate calculation techniques (e.g. ab initio molecular dynamics) without losing the level of accuracy necessary to gain new detailed insights, hardly reachable at the experimental level. Indeed, long-range and edge effects on the Fe4 structures and their easy axis of magnetization orientations have been evidenced as their different contributions to the overall macro-scopic behavior.