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

Abstract

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.

Understanding the role of solvent in regulating the crystal habit

“…From the results, it can be found that the observed induction times follow the Poisson distribution throughout the experiment time frame, giving a good fit (R 2 > 0.98) to the logarithmic form of eqn (2)(3)(4)(5)(6). The increased rate of primary nucleation was graphically observed from the slope of the distributions and quantified as a drop in the mean induction time.…”

“…[1][2][3] Crystal habits not only play an important role in downstream operations such as product separation, packaging, transportation and storage, but also affect the product's quality and solubility, thus influencing the API's bioavailability and efficiency. 2,4,5 A systematic study on the crystal habits of APIs can guide the optimization of the crystallization process, further improving the properties of the products. 6,7 Conventionally, the selection of suitable solvents and additives is the main route of crystal regulation.…”

A transferable force-field for alkali metal nitrates

“…experimental lattice dynamics. All previous force-fields show instabilities in the phonon spectra for at least some of the alkali nitrate polymorphs to which they were fitted except for those of Hammond [5]. This indicates that the structures obtained using previous force-fields were calculated using the full crystal symmetry and will distort away from the experimental crystal space group if the symmetry constraint is reduced or removed.…”

“…Several previous force-fields have been developed (e.g. Hammond et al [5] (Li, Rb), Ribeiro et al [6] (Li, Na, K, Cs), Xie et al [7] (Li, Na, K), Ni et al [8] (Li, Na, K), Mort et al [9] (Na, K) and Jayaraman et al [10] (Li, Na, K)). These have been developed for high temperature molten mixtures (Ribeiro, Jayaraman), solutions (Hammond, Xie, Ni), and defect chemistry (Mort) but no force-field has been developed that can be used across all of the alkali metal nitrates and none of them are really suitable for investigating crystallisation.…”

Synthesis and Characterization of New Sr3(BO3)2 Crystal for Stimulated Raman Scattering Applications

“…These crystals were revealed to possess many merits for SRS process, including larger Raman gain coefficient, stable thermal and mechanical properties, good chemical stability, non-deliquescence, and small volume etc. However, the relatively low anti-optical damage threshold and the long cut-off wavelength restricted their applications for SRS in the ultraviolet waveband [16,17].…”