Size-Dependent Reliability of Empirical Potentials for Global Optimization of Pt-Cu Bimetallic Clusters

Abstract

Empirical potentials (EPs) are widely used to pre-screen candidate structures before density functional theory (DFT) refinement, but their transferability to bimetallic clusters must be tested across size, composition, and parameterization. In this work, we compare the Gupta, Sutton-Chen (SC), and Finnis-Sinclair (FS) potentials for PtmCuN-m clusters at N = 13, 23, and 38 using CDE global optimization, geometric and segregation descriptors, and DFT assessment of selected EP minima. At N = 13 the three potentials converge on the same icosahedral motif, with the Gupta and SC candidates nearly degenerate in DFT energy and the FS candidate higher by 0.665 eV. At N = 23 and N = 38, however, the SC-derived structure becomes the lowest-energy DFT candidate , even though SC develops a descriptor-level segregation anomaly at N = 38. The FS potential accesses a distinct compact basin at N = 38 with a characteristic 143° dihedral signature, though this motif is not favored in the present DFT screening. These results show that empirical descriptors and DFT energetic competitiveness do not collapse into a single ranking, and that structural diversity from multiple EPs can broaden the Pt-Cu candidate pool when the resulting basins are filtered against first-principles calculations.