Polarization-dependent methanol adsorption on lithium niobate Z-cut surfaces

The adsorption of single methanol molecules on the lithium niobate (0001) surface, commonly referred to as Z-cut, is investigated using first-principles calculations. It is found that the binding energy for molecular adsorption on the negative surface (~1 eV) is about twice as large as for the positive surface. This difference is related to different bond strengths rather than electrostatics. Depending on the reaction path, lithium extraction from the negative surface may occur. This leads to an additional energy lowering by a few tenths of an eV. Larger energy gains are realized by dissociative adsorption, which is an activated process, however.