 |
Americium under pressure
This interesting investigation into 5f-electron behavior presented by Jean-Claude Griveau of the Joint Research Center of the European Commission at the Institute for Transuranium Elements, Karlsruhe, Germany, built upon the seminal work of Los Alamos’ Jim Smith and co-workers, which had verified superconductivity in americium (Am). In this instance, Griveau and his collaborators from Oak Ridge National Laboratory and Rutgers University investigated the effects of subjecting the element to high pressures—in the gigapascal (GPa) range, a clever notion underpinned by the hypothesis that one could influence atomic volume and, as a correlate, electronic behavior through this methodology.
Beginning from a plot of atomic volume against the number of f electrons in the actinide series and the classic chart of the itinerant-to-localized f-electron series of the actinides (with plutonium at the transition point), the jumping-off point was the observation that americium’s six 5f electrons are localized at zero applied external pressure.
|
Jean-Claude Griveau
A plot of atomic volume versus number of f electrons in the actinide series, relative to those of alpha and delta plutonium, is shown in the inset. A plot of changes in volume versus applied pressure shows how pressure affects atomic volume and subsequent properties.
Editor’s note: Pressure is an important variable in the chemistry and physics of materials, and Richard Haire of Oak Ridge National Laboratory reported on atomic-volume changes in americium in an earlier issue of ARQ (see 3rd/4th Quarters 2003). The plot of ΔV/V
0 for americum metal was adapted from S. Heathman et al. PRL 85 (2001) 2961.
|
