PROTON CONDUCTIVITY AND THERMODYNAMIC FEATURES IN THE HYDROGEN-BONDED MOLECULAR SYSTEMS

Abstract

The proton conductivity and thermodynamic features, arising from motions of the ionic and bonded defects, in hydrogen-bonded molecular systems have been investigated by the quantum-mechanical method and the transfer integral way in our model, in which the collective effect and the mutual correlation between the protonic and heavy ionic sublattices are specially considered. We first derived the equations of motion and its soliton solutions from the model Hamiltonian. The results obtained show that this model can simultaneously support motions of the ionic and bonded defects which are due to competition of the double-well potential and non-linearly coupled interaction between the protons and heavy ions. Thus we find out the mobility of the kink-antikink pair and electrical-conductivity of the proton transfer in the hydrogen-bonded systems exposed in an externally applied electrical-field through the dynamic equation of the kink-antikink pair and its solution in this model. For ice, the mobility and electrical conductivity of the proton transfer obtained are about (6.5 - 6.9)×10-6 m 2/ V · s and (7.6 - 8.1)×10-3(Ω · m )-1, respectively, which are in the domain of semiconductors and are basically consistent with experimental values for the crystal. Finally we calculate the free energy and specific heat of the systems with finite temperature by the model Hamiltonian and transfer integral way. The specific heat is also consistent with experimental data. This is a very interesting result.