Insights on finite size effects in Ab-initio study of CO adsorption and dissociation on Fe 110 surface

TL;DR

This study uses density functional theory to analyze how finite system size affects CO adsorption and dissociation on Fe 110 surfaces, highlighting the importance of system size and van der Waals interactions.

Contribution

It demonstrates the impact of system size on adsorption energies and dissociation barriers, emphasizing the need for larger models to accurately simulate dilute CO coverages.

Findings

Van der Waals interactions are crucial in small systems with high CO coverage.

Larger surface systems show significantly decreased dissociation barriers.

Surface elastic deformation is a general phenomenon affecting metal-hydrocarbon reactions.

Abstract

Adsorption and dissociation of hydrocarbons on metallic surfaces represent crucial steps to carburization of metal. Here, we use density functional theory total energy calculations with the climbing-image nudged elastic band method to estimate the adsorption energies and dissociation barriers for different CO coverages with surface supercells of different sizes. For the absorption of CO, the contribution from van der Waals interaction in the computation of adsorption parameters is found important in small systems with high CO-coverages. The dissociation process involves carbon insertion into the Fe surface causing a lattice deformation that requires a larger surface system for unrestricted relaxation. We show that, in larger surface systems associated with dilute CO-coverages, the dissociation barrier is significantly decreased. The elastic deformation of the surface is generic and can potentially applicable for all similar metal-hydrocarbon reactions and therefore a dilute coverage is necessary for the simulation of these reactions as isolated processes.