First principles study of isotope effect in hydrogen-bonded K3H(SO4)2: I — stable structures

The first principles calculations for K3H(SO4)2 (KHS) system are performed in order to determine its stable structure in the presence of the hydrogen or the deuterium in its hydrogen bond, and to discuss the origin of the large isotope effect in the KHS system. As a result, a reasonable value of the antiferroelectric interaction energy is obtained. It is also found that the position of the hydrogen is closer to the center of the hydrogen bond than that of the deuterium, based on the calculated results of the proton-position dependence of the oxygen–oxygen distance and on the experimental fact that the oxygen-oxygen distance in K3D(SO4)2 (DKHS) is larger than that in KHS.