An Examination of the Influence of Divalent Cationic Dopants on the Bulk and Surface Properties of Ba(NO₃)₂ Associated with Crystallization

The incorporation of divalent cationic species associated with the crystallization of Ba(NO 3 ) 2 related to nuclear waste storage issues is studied via the development and exploitation of a versatile and transferable empirical atom−atom forcefield for both mono- and divalent nitrates. Studies of binary and tertiary systems using Mott−Littleton and bulk supercell defect calculations reveals Ca 2+ ions to be the most energetically favored species for incorporation into the Ba(NO 3 ) 2 lattice over Sr 2+ and Pb 2+ ions. Incorporation modeling also confirms solid−solution behavior with an excellent Vegard’s Law fit. Tertiary systems involving Ba 2+, Ca 2+, and Sr 2+ ions are found to become less stable with increasing concentrations, notably of Sr 2+ . Morphological predictions using attachment and surface energy methods reveal a well-defined cube-octahedron habit, with negligible differences between Ba(NO 3 ) 2 and Sr(NO 3 ) 2 . Surface relaxation effects are found to be very small, with no apparent impact on the predicted crystal morphology, consistent with a very stable surface structure, reflecting both the close packing nature of the {100} and {111} habit faces and the strong in-plane Coulombic interactions between the cations and the anions. Examination of Sr 2+ incorporation onto Ba(NO 3 ) 2 crystal habit surfaces is in good agreement with experimental observations of the crystal morphology revealing preferential incorporation onto the {111}surfaces, with respect to the {100} surfaces, where the former case displays a layerlike packing of cations and anions that more easily effects the impurity incorporation process and hence prevents further growth, resulting in a more octahedral morphology.