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Path integral evaluation of H diffusion on Ni(100) surface based on the quantum instanton approximation
1Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026, People's Republic of China.
The Journal of Chemical Physics
|March 26, 2009
Summary
Quantum calculations reveal hydrogen diffusion on Ni(100) surfaces. Hydrogen tunneling dominates at low temperatures, with quantum surface atom motion hindering diffusion.
Area of Science:
- Surface Science
- Computational Chemistry
- Quantum Mechanics
Background:
- Understanding hydrogen diffusion on metal surfaces is crucial for catalysis and materials science.
- Previous studies often simplified surface atom dynamics or neglected quantum effects.
Purpose of the Study:
- To accurately calculate hydrogen diffusion coefficients on a Ni(100) surface.
- To investigate the role of quantum effects in hydrogen diffusion at various temperatures.
Main Methods:
- Quantum instanton approximation combined with path integral Monte Carlo and adaptive umbrella sampling.
- A 163-atom model treating hydrogen and surface Ni atoms with quantum mechanics, and bulk Ni atoms classically.
Main Results:
- High-temperature diffusion coefficients align well with experimental data.
- Hydrogen tunneling becomes the dominant diffusion mechanism below 80 K.
- A transition temperature of 70 K was identified, below which diffusion is nearly temperature-independent.
- Quantum surface atom motion was found to impede hydrogen diffusion compared to rigid or classical surfaces.
Conclusions:
- Quantum effects, including hydrogen tunneling and surface atom motion, significantly influence hydrogen diffusion on Ni(100).
- The study provides detailed insights into the quantum mechanisms governing surface diffusion.
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