All calculations are performed using PW-DFT as implemented in the Vienna Ab initio Simulation (VASP) package. The PBE functional and PAW pseudopotentials are used, along with the DFT-D3 scheme to account for the dispersion interactions. The applied convergence criteria for geometry (SCF) relaxation is set to 10 -5 ), the plane wave cutoff energy is 450 eV, and a 1 x 1 x 1 Γ-centered k-point grid is used for all the calculations. The calculations are spin-unrestricted. The MgO (100) surface is modeled using a 4 x 4 x 3 slab. Such a MgO slab contains six layers, of which the bottom two are fixed at the positions of the bulk, while the top four and the supported cluster are allowed to relax. A vacuum separation of at least 15 Å between repeating cells in z direction is added. The global and local minima search of the surface deposited clusters, as well as the most stable binding configurations of adsorbates on the clusters, are performed using several different techniques implemented in our in-house PGOPT package, as done in previous studies. Specifically, the lowest-lying minima of Pt 4 Ge x /MgO(100) are identified using the basin-hopping (BH) algorithm. BH starts from the generation of ten structures using a second-order bond length distribution algorithm (BLDA), and then sampled the potential energy surfaces of the supported clusters at 1500 K using a Monte Carlo scheme. Then, the most stable binding configurations of the adsorbates on the clusters are determined by optimizing 50 structures that are generated using the BLDA algorithm.