Density Functional Theory Study on Reconstruction and Reversible Transformation Processes of the ZZ57 Edge Structure in Carbon Materials: Effect of Na, K, and Ca.

Abstract

The edge structures of carbonaceous materials exhibit temperature-dependent behavior on the atomic scale, with variations in the relative ratios of zigzag, reconstructed 5-7 zigzag (ZZ57), and armchair edges observed at different temperatures. Nevertheless, the mechanisms underlying the interconversion of these edge structures and the influence of the surrounding metals remain unclear. This study investigates the reconstruction and reversible transformation processes of ZZ57 edge structures in carbon materials and examines the effects of different metal atoms (Na, K, and Ca) by using density functional theory. The simplified Z57 and A57 models are selected to simulate the microscopic reaction pathways at the isolated system level. Wave function analysis is conducted to determine the physical and chemical characteristics of ZZ57 edge structures and to predict the optimal adsorption positions of the metal atoms. Results indicate that the ZZ57 edge structure reconstruction and reversible transformation are exothermic reactions that proceed favorably in the forward direction. Analysis of the ten-membered ring in the transition state structure shows that the average bond order of the C-C bond is lower than that in the benzene ring system. Thermodynamic analysis shows that Na, K, and Ca atoms reduce the chemical equilibrium constant, thereby hindering the progress of the reactions. These findings not only provide specific theoretical insights into the transformation of the ZZ57 edge structure but also offer guidance for the precise design of carbon edges and the development of practical carbon materials.