Proton transfer in ice

Abstract

Born—Oppenheimer energy surfaces for proton transfer in H 2O cubic ice are calculated using gradient-corrected density-functional theory. Recombination of a pair of H 3O + and OH − ionic defects is found to occur without barrier for both first-neighbor and second-neighbor pairs. The energy barriers for proton transfer in the configurations (H 2OHH 2O)+ and (OHHOH) − are calculated to be only 0.069 and 0.058 eV, respectively. Relaxation of the atomic coordinates is found to be critical in determining the magnitude of the energy barriers. The relaxed geometries are not consistent with a solitonic description of the proton motion.