Large-scale first-principles DFT calculations on metallic nanoparticle catalysts
Abstract:
Controlling the shape and size of metallic nanoparticles (NPs) is a crucial challenge in catalyst development. Miniaturization of the NPs can enhance catalytic activity and reduce the usage of noble metal, while extremely small particles (e.g., sub-nano particles) have distinct differences electronic structures and stabilities compared to larger “nano” particles.
First-principles density functional theory (DFT) calculation is a powerful tool for investigating atomic and electronic structures of materials, but conventional DFT applications have been limited to small systems, comprising tens to hundreds of atoms due to significant computational costs. In this study, using our large-scale DFT calculation method in the CONQUEST code [1], we investigate the size and site dependencies of atomic and electronic structures in metallic NPs of a few nanometers in diameter, which is comparable to particle sizes in practical applications.
We optimized the structures of the NPs with diameters ranging from 0.5 nm (13 atoms) to 5.5 nm (3871 atoms) and found that the electronic structure of the NPs becomes metallic when particle sizes become larger than about 2 nm. Clear site dependence of local density of states was found in large NPs, particularly for atoms at the vertex and in the (111) face. To analyze massive data calculated for large systems efficiently, we have proposed a method for quantitatively and systematically comparing differences in local electronic structures in large systems by statistical analysis [2]. With this method, we analyzed the interactions between the NPs and the oxide substrate, summarizing which atom in the NP is affected by the substrate how largely. The relationship between the analyzed results and the catalytic properties were also investigated.
[1] A. Nakata, D. R. Bowler, T. Miyazaki, J. Phys. Soc. Jpn. 91, 091011 (2022).
[2] S. Li, T. Miyazaki, A. Nakata, Phys. Chem. Chem. Phys. 26, 20251 (2024).