Adsorption of water on an MgSO₄(100) surface: A first-principles investigation

The adsorption properties of water molecules on an MgSO₄(100) surface were investigated by using density functional theory (DFT) and supercell models. Optimized stable geometries of one and more than one water molecules adsorbed on an ideal MgSO₄(100) surface were obtained. The configurations with water molecules adsorbed on atoms of the second and third atomic layers of the MgSO₄(100) surface are quite stable. After adsorption, the separations between both the adjacent Mg atoms (R _Mg-Mg) and the adjacent O atoms of the surface (R_O-O) increase, which indicates that the MgSO₄(100) surface starts to deliquesce. In addition, water molecules are more likely to adsorb onto a defective surface rather than an ideal surface. Mulliken population analysis suggests that fewer charges transfer to the water molecule from the Mg atom of a defective substrate. Finally, Raman spectra were calculated for 0.5, 1, and 2 ML (ML=monolayer) water adsorbed on an MgSO₄(100) surface, which is helpful for further related experiments. Surface factors: The adsorption properties of water molecules on an MgSO₄(100) surface are studied by using density functional theory (see picture). The configurations of water molecules adsorbed on atoms of the second and third atomic layers of MgSO ₄(100) are quite stable. In addition, water molecules preferentially adsorb onto a defective surface.