A Further ¹H NMR Study on Cubic H_xWO₃: Reasons for the Apparent “Prefactor Anomaly”

Abstract

NMR studies of the cubic hydrogen bronze Hx WO3 have confirmed the hydrogen location proposed by Dickens et al. The diffusion of protons is limited by the availability of a framework of suitable oxygen sites and was found to contain elements of reduced dimensionality. The activation energy is of the order of magnitude of 40–50 kJ/mol, and the preexponential factor amounts to about 10‐13 s as usual. A “prefactor anomaly” observed in several other studies may arise if the dimensionality of the motion is not considered. Comparison with hydrogen bronzes HxMoO3 is discussed.