  Dangerous radioactive waste leftover from the Cold War era nuclear weapons
production continues to contaminate sixteen sites around the United States.
Although many challenges and obstacles exist in decontaminating these sites,
two particularly difficult tasks associated with cleanup of this waste are
extracting and separating actinide elements from the remainder of the solution,
containing other actinide elements and non actinide elements. Developing
effective methods for performing these separations is possible by designing new
chelating agents that form stable complexes with actinide elements, and by
investigating the interactions between the chelating agents and the actinide
elements. In this work, new chelating agents (or ligands) with potential to
facilitate the separation of radioactive waste are designed for Th, Pa, and U
using relativistic Density Functional Theory (DFT) inconjunction with a
high-throughput algorithm. We show that both methodologies can be combined
efficiently to accelerate discovery and design of new ligands for separation of
the radioactive actinides. The main hypothesis that we test with this approach
is that the strength of secondary coordination sphere (SCS) can be tuned to
increase the selectivity of binding with different actinides. More
specifically, we show that links that connect two of the catecholamide ligands
via covalent interactions are then added to increase the overall stability of
the complex. The effect of increase in the selectivity is also observed when
non-covalent interaction is used between ligands. We apply this approach for
Th, Pa, and U, and discover linkers that can be used with other ligands.
