Quantifying the Impact of Electric Fields on the Local Structure and Migration of Potassium Ions at the Orthoclase (001) Surface

Developing an understanding of the response of mineral/waterinterfacesto applied electric fields is central to detecting and interpretingsignatures of interfacial processes in the subsurface. Here, we focusdensity functional theory calculations on understanding K+ cation binding and migration across the (001) surface of orthoclasefeldspar under various applied electric fields with and without surfacehydration. The calculations reveal how water ligands labilize surfaceK(+) cations for migration while also increasing their sensitivityto electric field effects on the binding energy at different surfacesites. The calculations also show how the direction and strength ofthe electric field systematically affect surface cation mobility,sorption, and hydration behavior. Specifically, electric fields directedtoward the surface reduce the energy gap between the different surfacepotassium sites, favor hydration, and shorten K+ residencetime at their crystallographic site. The findings help fill a majorknowledge gap in the impact of electric fields on mineral/water interfacestructure and dynamics more generally, featuring, in this case, acommonly found type of feldspar involved in a multitude of atmosphericand geochemical processes.