Importance sampling within configuration space integration for adsorbate thermophysical properties: a case study for...

Area of Science:

• Surface science
• Computational chemistry
• Statistical mechanics

Background:

• Calculating partition functions is crucial for understanding adsorbate behavior on catalytic surfaces.
• Conventional methods often rely on the harmonic oscillator approximation, which can be inaccurate for complex systems.
• Accurate computation of adsorbate dynamics is essential for designing efficient catalysts.

Purpose of the Study:

• To develop and present a novel, efficient computational strategy for anharmonic partition functions.
• To compare the efficiency of importance sampling against conventional Monte Carlo methods.
• To investigate the anharmonic nature of methyl (CH3*) motion on a Ni(111) surface.

Main Methods:

• Implementation of an importance sampling strategy for computing partition functions.
• Comparison of computational efficiency with conventional Monte Carlo simulations.
• Application of the new method to the CH3* on Ni(111) system.

Main Results:

• Importance sampling demonstrated significantly higher computational efficiency compared to conventional Monte Carlo.
• The motion of methyl adsorbates relative to the Ni(111) surface was found to be anharmonic.
• Anharmonic calculations yielded significantly higher entropy values than those predicted by the harmonic oscillator model.

Conclusions:

• The developed importance sampling strategy offers a more efficient approach for anharmonic partition function calculations.
• The methyl/Ni(111) system exhibits significant anharmonicity, impacting thermodynamic properties.
• The new method, integrated into the ADTHERM package, provides a valuable tool for surface science research.