The pseudospin-electron model is formulated for the description of the correlated proton-electron charge transfer in the complex with hydrogen bonds. The energy spectrum of the model is obtained. The ground state diagram is built. The frequency dependence of the real part of conductivity is calculated. The time evolution of the proton and electron transfer along the hydrogen bond is studied. The time dependences of the mean occupancies of proton positions and electron states are obtained by solving the equations of motion for the density matrix components. The conditions, at which the motion of the proton and electron charges are mutually correlated, are considered.

We focus on the features of spectra and diagrams of states obtained via exact diagonalization technique for finite ionic conductor chain in periodic boundary conditions. One dimensional ionic conductor is described with the lattice model where ions are treated within the framework of "mixed" Pauli statistics. The ion transfer and nearest-neighbour interaction between ions are taken into account. The spectral densities and diagrams of states for various temperatures and values of interaction are obtained. The conditions of transition from uniform (Mott insulator) to the modulated (charge density wave state) through the superfluid-like state (similar to the state with the Bose-Einstein condensation observed in hard-core boson models) are analyzed.

The electron spectrum of the KDP-type crystals has been investigated as a function of the external hydrostatic pressure using the tight-binding approximation. The joint density of electron states, real and imaginary parts of the dielectric permeability, refraction indices, the gyration coefficient, absorption and reflection coefficients for different polarizations of light are determined. Their pressure and frequency dependencies are investigated. The results are discussed by comparing them with the experimental data on piezooptic coefficients. The anomalous behaviour of the optical constants at the pressure p ≃ 17 kbar is due to the transformation of the hydrogen bond potential from a double minimum one to a single minimum one, where the proton is localised at the midpoint of the hydrogen bond.