Boson enhancement of finite-temperature coherent dynamics for deuterium in metals.

Abstract

Effects of coherent many-particle dynamics in providing local site density fluctuations at finite temperatures for hydrogen isotopes in metals are analyzed with tight-binding calculations based on a Hubbard Hamiltonian. These fluctuations increase with temperature, with average deuterium density, and with the magnitude of the site-to-site tunneling. Consequences of such density fluctuations for deuterium dynamics at high concentrations are evaluated within a self-consistent formulation for self-screening of the deuteron-deuteron interaction. This leads to a prediction of significant enhancement of diffusion at high concentration for bosonic species, and anomalous isotope effects for hydrogen diffusion. Extrapolation to the nuclear regime yields estimates of finite-temperature bosonic collective effects on the nuclear reaction rate between deuterons in stoichiometric PdD, yielding rates which are several orders of magnitude below recent experimentally inferred values.