Structural, electronic, and adsorbed properties of Be-rich nanoalloys: Be n Pt (n = 1–10) clusters

The Hume-Rothery alloy phases of the main-group elements are rather rare, of which the phase stability mechanisms are decided by the electronic effects. The intermetallic compound Be-Pt alloy is a member of this family, but structural and electronic characters of them at nanometer scale still remain unclear. In this work, the geometric structures, stabilities and electronic properties of Be_nPt clusters (n = 1–10) are first investigated using the method combining the genetic algorithm with density function theory (DFT). Benchmark calculations indicate that the PBE-D3 functional is reliable in predicting the energetic sequences of four isomers of Be₄Pt cluster compared to the high-level coupled cluster method. In general, the most structures of the alloy clusters can be obtained by replacing one beryllium atom in the pure beryllium (Be_m, m = 2–11) clusters with a Pt atom. We found that the Be₄Pt and Be₁₀Pt clusters are two very stable 8e/20e superatoms in this series, respectively, where the electronic structure of Pt atom is d¹⁰. Analyses of electrostatic potential surfaces show that these two clusters have significant σ-holes with most positive potential regions, which can be seen as binding sites with Lewis bases. When a CO molecule is adsorbed on the superatom clusters, the CO stretching frequency has a large red-shift and the bond length is slightly elongated, due to the electrons of the clusters transfer to the anti-bond π orbital of CO. This work gives inferences for further understanding structural characters of the binary alloy from the nanoscale view.