A density functional theory study of the alkali metal graphite intercalation compounds using model complexes

Abstract

To analyze the electronic state of alkaline metal-graphite intercalation compounds (AM-GIC), model complexes where two aromatic molecules coordinate to an alkaline metal center (Li, K, Rb, and Cs) were employed, and their geometry optimization, population analysis, and donor-accepter interaction analysis were performed using the density functional theory (DFT) with B3LYP level and Natural Bond Orbital (NBO). The distance of two aromatic ligands of each model complexes showed good agreement with the corresponding identity period of stage 1 AM-GIC. The electronic charges on alkali metal of model complexes and stabilization energies by electron donation from aromatic ligand to alkali metal were calculated by the population analysis.The theoretical study of the mechanism of ethylene origomerization that proceeds inside the graphite layers was also carried out at DFT with B3LYP level. The Cs-C bond formation through the combination of two cationic Cs+ (η2-H2C=CH2) while accepting electrons from graphite layers is proposed as the initiation reaction of the origomerization. Additionally, we found that the carbon chain elongation reaction holds promise to proceed smoothly with a free energy of activation (ΔG‡) 16.29 [kcal/mol] under the presence of the chemical species having Cs-C bond.