Particle motions in superionic conductors

Abstract

The motion of ions in Ca²⁺F₂⁻ has been studied by molecular dynamics. The results show that, at 2.525 g cm⁻³ and 1590 K, the F⁻’s have a constant of self‐diffusion of 2.6×10⁻⁵ cm² sec⁻¹ and the Ca²⁺’s form a stable lattice. It is found that half of the F⁻’s occupy the octahedral sites of the fcc Ca²⁺ lattice. The details of the self‐diffusion process is analyzed showing the presence of a wave‐vector dependent long relaxation time in the decay of 〈exp(ik⋅u(t) 〉, which is the Fourier transform of the displacement u(t) of the F⁻ ions.