The atomically smooth surface of cleaved K+-mica is a common substrate for investigations of various phenomena at the mineral water interface. In this study, K+- inner-sphere adsorption above tetrahedral substitutions in the mica structure is found to be more favorable than that in mica's ditrigonal cavities for both dehydrated and hydrated cleaved mica. The activation energy necessary to transfer K+ from the inner-sphere adsorption state to the outer-sphere adsorption state, in which K+ can presumably migrate parallel to the surface, is calculated to be 45-48 kJ/mol on hydrated cleaved mica. The K+ desorption state is predicted to be >13 angstrom above the mica surface.