High Spin Ground States in Matryoshka Actinide Nanoclusters: A Computational Study.

Inspired by the experimentally synthesized Na12 @[(UO2 )(O2 )1.5 ]208- ("Na12 @U20 ") cluster, we have explored computationally the substitution of the Na cations by many other metals. 6 other M12 @U20 systems are found to be stable (M=K+ , Rb+ , Cs+ , Ag+ , Mg2+ , Fe2+ ). For 3 of these (Mg2+ , Ag+ and Na+ ), the cluster can support a group 16 dianion at its center, forming a new type of Matryoshka ("Russian Doll") actinide nanocluster E@M12 @U20 (E=S2- , Se2- , Te2- , and Po2- ). These systems have 3-shell, onion-like geometries with nearly perfect Ih symmetry. Seeking to create clusters with very high spin ground states, we have replaced M by Mn2+ and U20 by Np20 and Pu20 , generating clusters with maximum possible S values of 80/2 and 100/2 respectively. Only in the presence of a central S2- , however, are these electronic configurations the most stable; the novel Matryoshka Pu nanocluster S@Mn12 @Pu20 is predicted to have the highest ground state spin yet reported for a molecular cluster.