A SIMPLE-MODEL FOR 0-DIMENSIONAL HYDROGEN-BONDING FERROELECTRICS AND ANTIFERROELECTRICS

A simple model is proposed to describe 0-dimensional hydrogen bonding ferroelectrics and antiferroelectrics. Our model is composed of two dimers, each containing an electron and a proton (or deuteron), placed parallel to each other. This model enables us to calculate important physical quantities of 0-dimensional hydrogen bonds such as self-consistent potentials and the ground states of the proton (or deuteron) and the electron in them. There exists a range of hydrogen-bond length where the self-consistent potential is symmetric with a double minimum for the hydrogen bond with proton but asymmetric for the hydrogen bond with deuteron. The well-known large isotope effect in ferroelectrics and antiferroelectrics with 0-dimensional hydrogen-bonds can be reproduced by this two dimer model.