Multi-scale Simulation of Equilibrium Step Fluctuations on Cu(111) Surfaces.

Harry Handoko Halim,Kouji Inagaki,Yuji Hamamoto,Septia Eka Marsha Putra,Ikutaro Hamada,Fahdzi Muttaqien,Yoshitada Morikawa

doi:10.1021/acsomega.0c05064

Harry Handoko Halim, Kouji Inagaki + Show 5 more

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https://doi.org/10.1021/acsomega.0c05064

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Abstract

Understanding the nature of active sites is a non-trivial task, especially when the catalyst is sensitively affected by chemical reactions and environmental conditions. The challenge lies on capturing explicitly the dynamics of catalyst evolution during reactions. Despite the complexity of catalyst reconstruction, we can untangle them into several elementary processes, of which surface diffusion is of prime importance. By applying density functional theory–kinetic Monte Carlo (DFT–KMC) simulation employed with cluster expansion (CE), we investigated the microscopic mechanism of surface diffusion of Cu with defects such as steps and kinks. Based on the result, the energetics obtained from CE have shown good agreement with DFT calculations. Various diffusion events during the step fluctuations are discussed as well. Aside from the adatom attachment, the diffusion along the step edge is found to be the dominant mass transport mechanism, indicated by the lowest activation energy. We also calculated time correlation functions at 300, 400, and 500 K. However, the time exponent in the correlation function does not strictly follow the power law behavior due to the limited step length, which inhibits variation in the kink density.

Highlights

Heterogeneous catalysts play essential roles in the world of chemical industries by participating in 80% of industrial catalytic processes.[1]
First-principles calculations and kinetic modeling are combined in the form of density functional theory−kinetic Monte Carlo (DFT−kinetic Monte Carlo (KMC)) simulation to investigate the equilibrium fluctuations of steps on Cu(111)
In order to include explicitly all possible structures generated during simulation, a cluster expansion (CE) framework is implemented by including various fcc and hcp clusters as a basis set

Summary

INTRODUCTION

Heterogeneous catalysts play essential roles in the world of chemical industries by participating in 80% of industrial catalytic processes.[1]. Behrens et al have shown experimentally that the intrinsic activity of Cu for methanol synthesis is proportional to the probability of stacking faults (including steps and kinks).[13] Theoretical studies showed that the steps and kinks on Cu surfaces can alter the thermodynamic and kinetic of intermediates during methanol synthesis from CO2, resulting in different adsorption states, reaction pathways, and product yields.[31,32] Based on these reasons, we performed DFT−KMC simulation employed with CE to elucidate the microscopic mechanisms of Cu surface diffusions related with defects such as steps and kinks.

COMPUTATIONAL DETAILS

RESULTS AND DISCUSSION

SUMMARY

■ ACKNOWLEDGMENTS

■ REFERENCES