Theoretical models that describe adsorption over a wide range of adsorbate coverage can advance the fundamental understanding of natural or technological phenomena at surfaces, such as corrosion, heterogeneous catalysis, nanoelectronics, and solar cells. Most quantum-chemical models of adsorption are limited to low coverage (&lt; 0.25 monolayer (ML)) due to the large expense of computations at high adsorbate concentrations, whereas many practical applications, such as industrial heterogeneous catalysis occur at intermediate to high coverages. To bridge this gap, we have developed a lattice-gas model of adsorption that includes both surface and subsurface sites in the solid and is fully parametrizable using density functional theory (DFT) or another electronic-structure method of choice. Introducing subsurface sites into lattice-gas models enables us to explore the conditions and mechanisms of subsurface adsorption, a phenomenon thought to play important roles in oxidation, reconstruction, and catalysis. We have applied this model to study the adsorption of atomic oxygen on the silver(111) surface as a function of coverage. Population distributions calculated from our model show that atomic oxygen starts to populate the subsurface at total coverage in excess of 1/4 ML and accumulates more in the second subsurface, i.e., the region between the second and third layers of silver, at total coverage in excess of 1/2 ML. Further, we apply the model to perform Monte Carlo simulations to investigate the competition between surface and subsurface adsorption under varying conditions of gas pressure, surface temperature, and adsorbate coverage. Our study shows that lattice-gas models offer a powerful theoretical approach to obtain insight into subsurface adsorption and its participation in surface phenomena.

Insight into subsurface adsorption derived from a lattice-gas model and Monte Carlo simulations of atomic oxygen on the silver surface

ACS Spring 2022

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