Theoretical Study Addressing the (Meta-)Stability of Bimetallic Nanostructures

• Applicant: Professor Dr. Axel Groß
• Subject Area: Theoretical Chemistry: Molecules, Materials, Surfaces ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 272517120

• Final Report Year: 2020

Final Report Abstract

In this project, the stability of bimetallic nano structures has been addressed in a combination of first-principles total energy calculations and kinetic Monte Carlo simulation. In a first step, we considered the vacancy mediated diffusion in PtAu/Au(111), PtRu/Ru(0001), AgPd/(Pd111) and InCu/Cu(001) single-atom surface alloys. The migration of the foreign atom in the host metal can only proceed when the vacancy and the foreign atom become nearest neighbors and thus exchange places. Depending on the specific combination of foreign atom and host metal, the barriers for the exchange of the vacancy and the foreign atom range from 0.1 eV to 1.4 eV which leads to the fact that diffusion of the foreign atom is possible at room temperature or only at temperature above 1000 K. If the barrier for the exchange between vacancy and the foreign atom is signficantly larger than the vacancy diffusion barrier in the host metal, as in the system PtAu/Au(111), then the foreign atom will practically become immobile even at high temperatures as the vacancy will rather switch places with the atoms of the host metal than with the foreign atom. Finally, our kMC calculations confirmed that the apparent multi-lattice-spacing jumps in the system InCu/Cu(001) observed in STM experiments are a consequence of the low temporal resolution of the STM imaging. These studies have been extended to address the meta-stability of bimetallic surface alloys with varying mixing ratios of the two metallic constituents. Preliminary results indicate that indeed the bimetallic structures observed in the experiment are frozen structures that correspond to equilibrium structures at the annealing temperatures used in the experiment.

Publications

• Water adsorption on bimetallic PtRu/Pt(111) surface alloys, Proc. R. Soc. A 472, 20160618 (2016)
  J. M. Fischer, D. Mahlberg, T. Roman, and A. Groß
  
• Influence of Step and Island Edges on Local Adsorption Properties: Hydrogen Adsorption on Pt Monolayer Island Modified Ru(0001) Electrodes, Electrocatal. 8, 530 (2017)
  S. Sakong, J. M. Fischer, D. Mahlberg, R. J. Behm, and A. Groß
  
• Improved DFT Adsorption Energies with Semiempirical Dispersion Corrections, J. Chem. Theory Comput. 15, 3250 (2019)
  D. Mahlberg, S. Sakong, K. Forster-Tonigold, and A. Groß
  
• Influence of local inhomogenities and the electrochemical environment on the oxygen reduction reaction on Pt based electrodes: A DFT study, J. Phys. Chem. C
  S. Sakong, D. Mahlberg, T. Roman, M. Li, M. Pandey, and A. Groß
  
• Vacancy assisted diffusion on single-atom surface alloys, ChemPhysChem
  D. Mahlberg, and A. Groß