The solid-state properties of uranium A historical perspective and review

TLDR

The study traces the historical development of uranium metallurgy, from early experiments aimed at optimizing its use as nuclear fuel in the 1940s, through the availability of single crystals in the 1950s and debates over α‑phase superconductivity in the 1960s, to extensive investigations of 5f electron behavior in the 1960s and 1970s. The authors aim to review the mechanical, electronic, and structural properties of uranium, focusing on the low‑temperature α‑phase. The review synthesizes current knowledge and outlines remaining challenges, drawing on experimental and computational insights into uranium’s solid‑state behavior. Computational studies established that 5f electrons are itinerant, and neutron diffraction revealed a subtle lattice distortion at 43 K in the α‑phase, interpreted as a charge‑density wave that accounts for many long‑standing anomalies.

Abstract

Abstract We review our current understanding of the mechanical, electronic and structural properties of the element uranium, with the focus on the low-temperature regime in which the α-phase is stable. We start with a historical perspective, as the need for understanding the metallurgy of uranium so that its use as a nuclear fuel in the late 1940s could be optimized led to an increasing number of experiments aimed at exploring the solid-state properties. This was further accelerated when single crystals became available in the 1950s and when the superconductivity of the low-temperature α phase became the subject of controversy in the 1960s. The late 1960s and 1970s saw a considerable effort towards understanding the nature of the 5f electrons around the uranium nucleus. The increasing availability of sophisticated methods in computational physics first showed in the 1970s that the 5f electrons should be treated as itinerant, and the decade ended with the observation (by neutron diffraction) of a subtle periodic lattice distortion at 43 K in the α phase. The observation of this distortion, which is ascribed to a charge-density wave, leads to an explanation for many of the anomalies seen in over 30 years' work on the α phase. The review ends with a description of our current understanding and the problems still outstanding.