Theoretical study on the interactions between the lignite monomer and water molecules

Quantum chemical calculations have been performed by using hybrid meta functional (M06-2X) to describe the hydrogen bonding interactions between the lignite monomer and water molecules. The characteristic and stability of water clusters in lignite monomer-water complexes were investigated and the solvent effects on geometries and hydrogen-bond energies were analyzed. The results indicated that the total hydrogen-bond energy gradually enhanced with increase of the number of water molecule because of hydrogen bonding cooperative interactions. The different features of water cluster were observed in the lignite monomer-water mixture. The significant changes in water clusters were not observed compared to the structures in gas phase, and the interaction energies decreased substantially. The length of hydrogen-bond was averaged due to solvent effect. The conclusion was consistent with the infrared analysis.