ISSN:
1432-0630
Keywords:
63.00
;
64.00
;
66.30
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Abstract Molecular dynamics simulations of the BaF2 fluoride crystal were carried out over a wide range of temperatures in order to study structural and transport characteristics in the low-temperature, the high-temperature superionic, and the molten state. The experimental temperature dependence of the lattice constant was taken into account. A sharp change in total energy of the system in the vicinity of T=1200 K indicates a phase transition to the high-temperature state with a transition energy ΔU=(18.8±0.2) kJ/mol which is close to the value of the latent heat Q=18.36 kJ/mol obtained experimentally at 1275 K. Calculation of the radial distribution functions g(r) shows that in the high-temperature superionic state the F− sublattice is already disordered while the Ba2+ sublattice stays regularly ordered, which keeps the crystal in the solid state. In the low-temperature state both sublattices are regularly ordered, and in the molten state both sublattices are disordered. The calculated diffusion constants of F− in the superionic state is about 10−9m2/s which is a typical value for superionic conductors. The temperature dependence of the diffusion constant obeys the Arrhenius equation. Higher statistical moments of the trajectories are used to characterise the type of ion movement.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00323845
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