Diffusion of hydrogen in transition metals

Abstract

The mobility of interstitial atoms is closely correlated with their vibrational behaviour. Not only can the classical (hopping) activation energy be evaluated with good accuracy from the vibrational spectrum, but also low temperature tunnelling rates are strongly related to vibrations. Because of their small mass interstitial hydrogen atoms constitute an ideal probe to study this correlation over a large temperature range (0 K < T < 300 K). Hydrogen atoms vibrate mainly with localized (optical) modes but also with strongly distorted lattice vibrations (short-wavelength acoustic modes). These vibrations lead to a "dressing" of the tunnelling element. More interesting, they determine the temperature dependence of the diffusion constant (at low temperatures together with electronic terms). Using a realistic description of the vibrations as input we calculate the diffusion constants quantitatively. We present results for hydrogen in niobium and in lutetium.

Proton transport in barium stannate: classical, semi-classical and quantum regimes

“…3,4 Hydrogen diffusion is a key process in a large number of systems, organic or inorganic. The pioneering ideas have been formulated by Marcus to describe the transfer of localized electrons in solutions.…”

The Electron and Occam’s Razor

“…A surprising effect is the difference in textures of newly formed phases: whereas the β-phase texture remains unchanged (100), that of α-phase becomes (110). The result is a significant increase in the concentration of defects, mainly dislocation walls at the phase boundaries, a/β, and β ↔ β+α decay is accompanied by profound rearrangement of Pd-D solid solution, leading to a significant increase in the dislocation density (up to 10 11 -10 12 cm −2 ).…”