Absolute rate of thermal desorption from first-principles simulation.

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• Understanding molecular desorption from surfaces is crucial for catalysis and thin-film growth.
• Accurate computation of desorption rates (γ) is challenging, especially across different coverages and temperatures.
• Existing methods often rely on approximations or limited experimental data.

Purpose of the Study:

• To present a novel first-principles simulation technique for calculating the absolute desorption rate (γ) of adsorbate molecules from surfaces.
• To validate the technique's applicability for any surface coverage and temperature, given specific conditions.
• To assess the accuracy of the generalized gradient approximation (GGA) for D(2)O adsorption on MgO(001).

Main Methods:

• Utilizing an exact expression for desorption rate (γ) based on the difference in chemical potentials between gas-phase and adsorbed molecules.
• Computing the potential of mean force via constrained first-principles molecular dynamics.
• Applying the technique to D(2)O on the MgO(001) surface at low coverage using GGA.

Main Results:

• The study successfully computed the absolute desorption rate (γ) for D(2)O on MgO(001).
• Comparisons with experimental temperature-programmed desorption data provided an assessment of GGA accuracy.
• The developed technique demonstrates validity when surface thermal equilibration rates exceed the desorption rate.

Conclusions:

• The presented first-principles simulation technique offers a robust method for determining molecular desorption rates.
• The findings contribute to a better understanding of D(2)O adsorption on MgO(001) and the performance of GGA.
• This computational approach can be extended to other adsorbate-surface systems for accurate desorption rate predictions.