Abstract
The adsorption mode of ammonia on the (001) surface of kaolinite was explored using the periodic DFT/PBE-D3 method. The thermodynamics and electronic properties such as adsorption energy, bond lengths and density of states were calculated to investigate the adsorption mechanism. Calculated adsorption energies were negative for ammonia-kaolinite complexes indicating a favorable exothermic process. The corrections of the van der Waals dispersion play an important role in stabilizing ammonia-kaolinite interactions. The maximum surface coverage is found to 4.3 molecules/nm(2) . The geometric parameters, Bader charges and PDOS analysis results showed that ammonia is adsorbed on the surface (001) of kaolinite clay by a hydrogen bond, mainly through the electrostatic interaction between the hydroxyls group of the surface and the nitrogen atom of NH3 molecule. The analysis of the computed infrared spectra of free and adsorbed NH3 highlights the impact of adsorption on its characteristic stretching and bending modes.
[GRAPHICS]
.