Ag diffusion constant in RbAg4I5 and KAg4I5 determined by pulsed magnetic gradient NMR

Abstract

We have measured the diffusion constant D of 109Ag in the temperature range 150 to 300 K in RbAg4I5 and KAg4I5 by nuclear magnetic resonance employing the pulsed magnetic gradient method. The activation energies are 0.12 ± 0.01 eV for the α phase in both compounds and 0.16±0.01 eV and 0.18±0.01 eV for the β phases of RbAg4I5 and KAg4I5, respectively. At least in KAg4I5 our data reveal a discontinuous change of D at the α→β transition. In terms of the Haven ratio a decrease from 0.51 to 0.39 is observed for the α→β transition. This decrease is taken as evidence for an increased correlation of the Ag motion in the β phase.