Density functional theory was used to study the stepwise decomposition of adsorbed ethylene on Pd(1 0 0) aiming to better understand the evolution behavior and illustrate the plausible carbon formation routes. The structural and energetic properties of various C-H and C-C bond scission reactions were calculated and C-H bond breaking seems always favorable for the same species. CH2CH and CH fragments were verified as likely intermediates theoretically, in accordance with previous experiments. Three possible pathways for the formation of carbon monomer were proposed based on the analysis of the reaction network and they all feature the generation of CH as the rate-limiting step. There exists some structure sensibility for ethylene transformation on Pd catalyst on account of the notable difference between the results on Pd( 1 0 0) with that on Pd( 1 1 1) and Pd( 2 1 1) reported recently. (C) 2014 Elsevier B.V. All rights reserved.