Search

The ground-state binding energies of deep impurities (Cu, Ag, Au, Zn, Cd, Hg, Ni, Fe, S, Se, Te) in Ge 1− x Si x (0≤ x ≤0.35) have been experimentally determined on the basis of Hall measurements. It is shown that the average activation energies (Δ E ) of different charge states of the impurities in Ge 1− x Si x increase approximately linearly with silicon concentration in agreement with the concept of virtual crystal model for alloys. Random-alloy splitting of the deep impurity levels due to different local surroundings of the defect core in the crystals is discussed. Obtained results allow binding energies and possible charge states of the investigated deep impurities in all Ge 1− x Si x system to be determined.

Influences of the Aharonov-Bohm flux on the optical polarons in the molecular-crystal model with the dispersion term in a ring is considered. The results show that the lattice displacement of the self-trapped state, the self-trapped potential well of the electron and the width, the peak and the binding energy of the polaron are dependent upon the Aharonov-Bohm flux.

A simple kinetic TLK crystal model is studied, where growth and evaporation take place by attachment and detachment of atoms at kink sites along steps. Assuming the steps to run up and to the right exclusively, the model is mapped onto the 6-vertex model, where the step lines correspond to the lines obtained by marking the arrows pointing down and to the left. (Since vertex 2 is absent, the model is actually a 5-vertex model). The growth process is described by an exact master equation, which is then solved for small-size versions of the model; the growth rate is calculated in terms of the kinetic coefficients. The limit for large sizes is discussed.

An extended molecular crystal model is put forward for the mechanism of high-temperature superconductivity in the typical perovskite-like structures Ba x La 2− x CuO 4 and Ba 2 YCu 3 O 6.5+1.5 x , 0 x ≲ 0.4. It is shown that the Jahn-Teller effect of the Cu 2+ cation brings about an attractive pairing interaction between the hybridized 3 d 9 electron states. The critical temperature is estimated and compared with the available experimental data.

The generating coefficients of lattice Green functions have been calculated for the (111) face of f.c.c. crystal. The crystal model takes account of only central force between nearest neighbours. Phonon dispersion relations and mean correlated displacement value between nearest and next-nearest neighbours are given.

The Hubbard Model of electron correlation effects in solids is unified with Holstein's molecular crystal model for small polarons as a first step in studying electron-phonon coupling in π-bonded organic solids. Some implications of the electron-lattice coupling on both the single particle excitation spectrum and the effective Heisenberg exchange energy are discussed.