A quantum approach to the study of D and L defects in h-bonded systems was extended. The protons were considered to be quantum particles, and account was taken of both intra-site and inter-site tunnelling. It was noted that it was still an open question whether tunnelling was significant in H-bonded systems. Many papers had given very different estimates of the tunnelling matrix elements (0.1 to 100/cm). Other experiments indicated large proton fluctuation effects that could be explained only as a quantum phenomenon. Within the framework of the quantum approach, many-particle correlations could be taken into account in a more simple manner than in the classical method. The process of inter-site motion of D(L) defects depended upon the quantum-mechanically characterized polarity state of the system. That is, a defect could transfer from one site to another if the polarization states of these sites were suitable. It was shown that the ground state of the H-bonded system with a D(L) defect was a bound state of a kink-like polarization distribution (ionic defect) and a bell-like soliton that described the D-defect probability distribution. It was found that the energy of this state was always lower than the energy of a uniform spatial state

Y.Gaididei, N.Flytzanis, O.Yanovitskii: Solid State Ionics, 1995, 77, 20-3