Despite continuing and burgeoning interest in americium (Am) coordination chemistry in recent years, investigations of the electronic structures and bonding chemistry of high oxidation state americium complexes and their implications for minor actinide separation remain relatively less explored to date. Here, we used density functional theory (DFT) to create high oxidation states of americium but experimentally feasible models of Am(V) and Am(VI) complexes of phenanthroline ligand (DAPhen) as [AmO 2 (L)] 1+/2+ and [AmO 3 (L)] 1+ (L = 2,9-bis[(N,N-dimethyl)-carbonyl]-1,10-phenanthroline (oxo-DAPhen, L O ) and 2,9-bis[(N,N-dimethyl)-thio-carbonyl]-1,10-phenanthroline (thio-DAPhen, L S )), meanwhile comparing these with [UO 2 (L)] 2+ . On the basis of the calculations, the Am(V) and Am(VI) oxidation state are thermodynamically feasible and can be stabilized by DAPhen ligands. From a comparative study, the strength of thio-DAPhen in the separation of high oxidation state Am emerges better than does oxo-DAPhen, which relates to the nature, energy level, and spatial arrangement of their frontier orbitals. This study provides fundamental knowledge toward understanding the transuranic separations processes, which has implications in designing new, more selective extraction processes for the separation of Am from curium (Cm) as well as lanthanide.
The coupling between structural phase transformations and dislocations induces challenges in understanding the deformation behavior of metallic cerium at the nanoscale. In the present work, we elucidate the underlying mechanism of cerium under ultra-precision diamond cutting by means of molecular dynamics modeling and simulations. The molecular dynamics model of diamond cutting of cerium is established by assigning empirical potentials to describe atomic interactions and evaluating properties of two face-centered cubic cerium phases. Subsequent molecular dynamics simulations reveal that dislocation slip dominates the plastic deformation of cerium under the cutting process. In addition, the analysis based on atomic radial distribution functions demonstrates that there are trivial phase transformations from the γ-Ce to the δ-Ce occurred in both machined surface and formed chip. Following investigations on machining parameter dependence reveal the optimal machining conditions for achieving high quality of machined surface of cerium.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.