Assessing Low-Cost Computational Methods against Structural Properties and Size Effects of Pt nanoparticles

An evaluation of the performances of several known low-cost methods for the reproduction of structural features of differently sized Pt nanoparticles (NPs) is presented. The full density functional theory PBE-dDsC functional (within the plane-wave formalism) was employed to benchmark the semiempirical tight-binding DFTB and GFNn-xTB (n = 0, 1, 2) and the reactive force-field ReaxFF. Performances were evaluated by comparing several size-dependent features (such as relative stabilities, structural descriptors, and vibrational features) computed with the different methods. Various structures (ordered and amorphous) and sizes (from Pt-13 to Pt-561) were considered in the datasets. ReaxFF molecular dynamics (MD) was employed to achieve the amorphization of cuboctahedral Pt-147, Pt-309, and Pt-561 geometries, which were subsequently optimized with both the low-cost methods and the DFT reference, within a multilevel modeling approach. The structures were further annealed with GFN0-xTB MD. While DFTB performs quite well over all the selected structures, GFN2-xTB and the cheaper GFN0-xTB show a general predilection for amorphous geometries. The performances of GFN2-xTB are found to worsen with the increasing size of the system, while ReaxFF and GFN0-xTB undergo the opposite trend. We suggest that the semiempirical DFTB (and within certain limitations GFN0-xTB and ReaxFF) could be suited for fast screening through amorphous big-sized Pt NPs.