Density functional theory (DFT) calculations have been used to elucidate the influences of the surface properties of Pd-Au(100) on the conversion of ethylene to ethylidyne at the molecular level. To find out the effects of the surface properties on the conversion of ethylene, three different Pd-Au(100) surface configurations-the second nearest neighbors (denoted as PdsnAu), the first nearest neighbors (denoted as PdfnAu), and the fourth nearest-neighbor palladium island (denoted as PdislAu) are selected as the model catalyst surfaces to represent the Pd-Au(100) surfaces. The quantitative energy barriers of all reactions involved in the network of conversion of ethylene to ethylidyne on three different Pd-Au(100) surfaces were calculated. The possible pathway of this process on the Pd-Au(100) surface is suggested as (M1) ethylene -> vinyl -> vinylidene -> ethylidyne and (M2) ethylene -> ethyl -> ethylidene. ethylidyne. M2 is preferable on PdsnAu, while on PdfnAu and PdislAu the pathway of M1 competes with M2. The results indicate that the morphology of the surface Pd atoms on the surface affect the conversion of ethylene to ethylidyne. (C) 2017 Elsevier B.V. All rights reserved.