First principles study of isotope effect in hydrogen-bonded materials

First principles calculation for K3H(SO4)2 is performed to investigate the origin of the isotope effect in hydrogen-bonded (anti) ferroelectric materials by taking account of the zero-point oscillation effects of the proton and the deuteron. The calculated proton potential surface is not a double-well-type, but it makes the positions of the hydrogen and the deuterium different. The shrinkage of the dipole moment due to the zero-point oscillation of the proton is also important. (author)