PNNL

Abstract

We have quantified the C-C lateral interactions on Fe (100) using a density functional theory (DFT) parameterized Lattice Gas Cluster Expansion (LG CE) model trained using 265 unique configurations spanning a C coverage from 0-1 monolayer (ML). Our LG CE model shows high predictive accuracy with a Leave Multiple Out cross validation (LMO CV) score of 10.2 and 16.6 meV/site for systems with and without the top two-layer of Fe atoms fixed. Electronic GS structures identified from the lattice gas model (including the structures at 0 and 1 monolayers), were further used to generate ab initio phase diagrams under a range of temperatures and pressures. Under low temperatures (500 K), the 0.88 ML structure is most likely to form on the Fe surface. Interestingly, our model identified a c (2 × 2) ordered structure at ½ ML, which correlates well with previous DFT studies for carbon adsorption on iron surfaces and matches with the experimentally observed LEED structure. Overall, the DFT parameterized energies for the C/Fe system including effects of coverage and configurational space can further help in developing multiscale models for various heterogenous reactions involving C-C and C-Fe interactions