The quantum simulation of metal-hydrogen systems and the analysis of diffraction experiments

Abstract

The path-integral simulation technique is used to study an empirical model for hydrogen and deuterium in niobium. This simulation method fully incorporates quantum effects, which are known to play an important role in the behaviour of hydrogen in metals, especially at low temperatures. It is argued that the density distribution of hydrogen is a key quantity in understanding metal-hydrogen systems since it depends sensitively on the metal–hydrogen interaction and since it is directly related to structure factors measured by diffraction experiments. We present simulation results for the density distribution of the niobium–hydrogen and niobium–deuterium systems in real space at 300,423, 500 and 700 K. We calculate the relevant structure factors and compare with existing diffraction data. We conclude firstly that the simulation results can be directly compared against diffraction data and such comparisons provide an important test of the interaction model on which the simulation is based and secondly that improved diffraction data are needed.