Nucleation and growth on defect sites: experiment-theory comparison for Pd/MgO(001)

Area of Science:

• Surface Science
• Materials Science
• Computational Chemistry

Background:

• Nucleation of metal clusters on oxide surfaces is primarily driven by defect sites.
• Existing rate equation models have been used to study these systems, deducing various energy parameters.
• However, the specific defects responsible for nucleation remain largely unidentified.

Purpose of the Study:

• To investigate and identify specific surface defects responsible for metal cluster nucleation on oxide surfaces.
• To compare ab initio calculations of defect energies with experimental nucleation density data.
• To refine nucleation density predictions using validated theoretical energy values.

Main Methods:

• Application of rate equation models to nucleation density experiments.
• Survey and comparison of various ab initio calculation methods for defect energies.
• Prediction of nucleation densities using calculated defect energies for Pd/MgO(001).

Main Results:

• Significant divergence observed among calculated defect energy values from different ab initio methods.
• New nucleation density predictions were generated using calculated values.
• Singly charged F(s)(+) centers and neutral divacancies emerged as strong candidate defects based on agreement with experimental data.

Conclusions:

• The singly charged F(s)(+) center and neutral divacancy are identified as likely dominant defects for palladium nucleation on MgO(001).
• Pd/MgO(001) nucleation density predictions using these defect models show good agreement with experimental results.
• These specific surface defects warrant serious consideration in future studies of metal-oxide nucleation.