Quantum chemical calculations of intracell potential profile in superionic transition range in LaF3
Annotatsiya
The results of quantum chemical calculations of the potential profile in the LaF3 crystal lattice in the range of superionic phase transition are presented for clusters containing 24 to 1200 ions. It is found that the values of formation energy E a of vacancy-interstitial fluoride ion defects and potential barriers E d hindering the movement of fluoride ions and determining the efficiency of charge transport in the lattice grow monotonously from the minimum values E a = 0.12 eV and E d = 0.22 eV for a 24-ion cluster to the maximum E a = 0.16 eV and E d = 0.26 eV for clusters of 576 and 1200 ions. It is shown that the values of E a and E d obtained for the dielectric phase (T < T c) are several times the values of E a and E d for the superionic state (T ≥ T c) of LaF3. The values of E a and E d obtained by quantum chemical calculations from clusters of 576 and 1200 ions agree well with energies E a and E d obtained from the analysis of the data of the Raman and quasielastic light scattering.