Atomic-Scale Investigation of Methane Adsorption on Ni(111): Electronic Structure, Charge Redistribution, and Surface Stability Using Density Functional Theory

Methane (CH₄), the principal component of liquefied natural gas (LNG), can interact with metallic surfaces encountered in energy-related systems. Understanding these interactions at the atomic scale is important for evaluating interfacial behavior and establishing reference models for methane–metal adsorption. In this study, the adsorption of a single CH₄ molecule on a clean Ni(111) surface was investigated using density functional theory (DFT) with the generalized gradient approximation and Perdew–Burke–Ernzerhof exchange–correlation functional (GGA-PBE), including D3 dispersion corrections, as implemented in QuantumATK 2023. Geometry optimization showed that CH₄ retained its tetrahedral configuration, with a C–H bond length of approximately 1.11 Å and an equilibrium C–Ni separation of approximately 3.21 Å. The Ni–Ni interatomic distance changed only slightly from 2.49 to 2.48 Å, indicating limited structural relaxation. The calculated adsorption energy was −0.15 eV, suggesting energetically favorable but weak, non-dissociative adsorption. Density-of-states (DOS) and projected density-of-states (PDOS) analyses indicated limited changes in the electronic structure near the Fermi level and weak electronic coupling between CH₄ and the Ni surface. Bader charge analysis yielded a reported net charge difference of approximately +0.008 e for the adsorbed molecule, consistent with limited interfacial charge transfer. The combined structural, energetic, and electronic results support a predominantly physisorbed molecular configuration. These findings provide an atomic-scale reference for methane adsorption on clean Ni(111) and may support future comparisons with defective, irradiated, or otherwise modified nickel surfaces.