Solubility Phase Diagram of the Ternary System LiCl-MgCl2-H2O and Li2SO4-MgSO4-H2O at 348.15 K

The solubility isotherms of the ternary systems LiCl-MgCl2-H2O and Li2SO4-MgSO4-H2O were elaborately redetermined at 348.15 K using an isothermal equilibrium method. The compositions of solid phases were confirmed using the Scherinemakers' wet residue method. The ternary system LiCl-MgCl2-H2O is of a complex type with double salt LiCl center dot MgCl2 center dot 7H(2)O((s)) formed at 348.15 K, it gives the data of two invariant points for the first time and points out the boundary of three univariant curves and three crystallization fields corresponding to LiCl center dot H2O(s), MgCl2 center dot 6H(2)O((s)), and LiCl center dot MgCl2 center dot 7H(2)O((s)) clearly, which is more complete and accurate than the results in the literature at 348.15 K. In the ternary system Li2SO4-MgSO4-H2O, there are three solubility branches corresponding to the solid phases MgSO4 center dot nH(2)O((s)) (n = 6 and 1) and Li2SO4 center dot H2O(s); the phase field of MgSO4 center dot H2O(s) overlaps with the phase field of MgSO4 center dot 6H(2)O((s)), this finding indicates that the phase MgSO4 center dot H2O(s) is stable and MgSO4 center dot 6H(2)O((s)) is metastable; moreover, it gives the true equilibrium solubility data for MgSO4 center dot H2O(s) in the binary system MgSO4-H2O and the ternary system Li2SO4-MgSO4-H2O at 348.15 K and an invariant point which can point out the boundary of the two phase fields of MgSO4 center dot H2O(s) and Li2SO4 center dot H2O(s) definitely

The investigation of structure and IR spectra for hydrated potassium ion clusters K

The hydration of K+(H2O)n has been widely studied and believe to be important for understanding solvent properties in biological and chemical systems. However, understanding the structure and the spectrum information K+(H2O)n with changing n is limited. Here, we investigated the clusters K+(H2O)n=1–16 and further studied the IR spectrums of the most stable clusters with density functional theory. The configuration, bond length, vibration frequency were given out. It shows that K+(H2O)8(H2O)n, a distorted square antiprism in inner layer, is the main configuration with hydration distance rK - OI 0.296 nm when the hydration number n is bigger than 8. The saturated hydration number is 8 in the first hydration layer and the water molecules of the second hydration sphere have little effect on the inner ones when n> 8. A detailed classification about the hydrated water molecules was made according to the role of acceptor or donor hydrogen bonding in clusters. The vibration frequency of the different kinds of water molecules were also detailly identified. The results are valuable for further determination of the K+(H2O)n clusters in aqueous solutions

Solution Structure of Energy Stored System I: Aqua-B(OH)₄^–: A DFT, Car–Parrinello Molecular Dynamics, and Raman Study

A systematic study on the structure, stability, and Raman spectra of the metaborate anion hydrated clusters, B­(OH)₄^–(H₂O)_<i>n</i>, (<i>n</i> = 1–15) was carried out by DFT in both gaseous and aqueous phase at the B3LYP/aug-cc-pVDZ level; all of these stable configurations were described, and the most stable hydrated clusters were chosen. The hydrogen bonds in those hydrated clusters were described in three different items: symmetrical double hydrogen bonding (DHB), single hydrogen bonding (SHB), and interwater hydrogen bonding (WHB). The distance of SHB is shorter than that of DHB, and multiple SHBs are more stable than a single DHB. In small size clusters (<i>n</i> ≤ 5), a structure with more DHBs is more stable than other arrangements. With continued increase in size, more SHBs were found in the first hydration sphere: when <i>n</i> ≥ 9, only SHBs can be found, and when <i>n</i> ≥ 12, a full hydration structure is formed with 12 SHBs and a hydration number of 10–12. The Car–Parrinello molecular dynamics simulation shows that only the first hydration sphere can be found, and the hydration number of B­(OH)₄^– is 9.2 and the hydration distance is 3.68. The total symmetrical stretching vibration of B­(OH)₄^– in hydrated B­(OH)₄^–(H₂O)_<i>n</i> is blue shifted with increasing cluster size. After consideration of hydration, the calculated characteristic frequencies are in accord with the experiment characteristic frequency of B­(OH)₄^–

Ion association in lithium metaborate solution: a Raman and <i>ab initio</i> insight

<p>Ion association and hydration clusters in aqueous lithium borate solution are extremely important to understand some extraordinary properties of lithium borates. In the present work, polyborate distribution in aqueous LiBO₂ solution was investigated through Raman and thermodynamics equilibrium analysis. Geometry and stability of hydrated clusters LiB(OH)₄(H₂O)<i>_n</i> up to <i>n</i> = 8 were calculated at the B3LYP/aug-cc-pVDZ level. Three different types of ion association, namely, contact ion pairs (CIP), solvent-shared ion pairs (SIP) and solvent separated ion pairs (SSIP) were obtained; characteristics of all of these stable configurations were determined, and the most stable hydrated clusters were chosen. Then the mechanisms of ion aggregation and crystal nuclei formation in the LiB(OH)₄ solution were proposed. The tight four-hydrated sphere of Li⁺ makes it difficult for the dehydrated form of its first hydration sphere to from a CIP, which is the passible reason that lithium borate always has a large super-saturation degree.</p

<i>Ab Initio</i> Investigation of the Microspecies and Energy in Hydrated Strontium Ion Clusters

<p>Quantum chemistry calculations were used to study the structure and energy of strontium (Sr) ion hydrated clusters [Sr(H₂O)₁₋₂₅]²⁺. The saturated hydration number of the first hydration layer of Sr²⁺ was 8, and the hydration distance was 2.58 Å. The second hydration layer had 1–9 hydration numbers, and the hydration distance was in the range of 4.4–4.6 Å. This work also developed the relationship between the thermodynamic data (average water binding energy <i>E_n</i> and successive water binding energy Δ<i>E_n,n</i>₋₁, etc.) of the aforementioned low-energy structure and the hydration structures. The first hydration layer was formed by the strong electrostatic interaction between Sr²⁺ and water molecules, and the decrease in Δ<i>E_n</i>_,<i>_n</i>₋₁ was relatively large. Hydrogen bonds were formed between water molecules of the second hydration layer and water molecules of the inner layer, and the decrease in Δ<i>E_n</i>_,<i>_n</i>₋₁ was relatively small. When one water molecule was added beyond the second hydration layer, Δ<i>E_n</i>_,<i>_n</i>₋₁ was close to the hydrogen bond energy 8.88 kcal/mol (37.1 kJ/mol) of dimer water molecule, indicating that there was very weak interaction between Sr²⁺ and the water molecules beyond the second hydration layer.</p