Ion association characteristics in MgCl₂and CaCl₂aqueous solutions: a density functional theory and molecular dynamics investigation

Ca2+‐Cl− Association in Water Revisited: the Role of Cation Hydration

“…[12] In this study,t he role of cation hydrationi nt he pair dissociation was considered and am echanism based on the entrance of as ixth water molecule in the Ca 2 + solvation shell occurring at an interionic distance of 3.5 was proposed. Dai et al used Density Function Theory (DFT) and molecular dynamics to investigate ion pairing of calcium chloride in water clusters and in solution, [13] and concluded that contact ion pairs may not be neglected, even though they are less frequent than solvent shared ion pairs. Wang et al used the same approacht oa nalyze the stability of highorder Ca-Cl complexes( with several chloride ligands) in concentrated mixed calcium and lithium chloride solutions.…”

High-Order Ca(II)–Chloro Complexes in Mixed CaCl2–LiCl Aqueous Solution: Insights from Density Functional Theory and Molecular Dynamics Simulations

“…Classical MD simulation, which generally deals interatomic interactions with classical two- or three-body interatomic potentials, has been proven to be an efficient tool and is used extensively to investigate various properties of larger systems. − Therefore, classical MD simulation was used to investigate the presence and structural characteristics of high-order Ca–Cl complexes in concentrated LiCl brine, and all MD simulations were performed using the DL_POLY_4.03 software package. , In this study, the interatomic interactions between water and ions were defined by pairwise potentials, where van der Waals interactions were modeled through the Lennard-Jones (LJ) potential, whereas the electrostatic interactions resulted from the partial charges on each atomic center. The LJ potential was used in previous MD study on alkaline earth metal–chloride complexation in aqueous solution. ,,, There are several successful applications of the extended simple point charge (SPC/E) water model for brine systems, , so the SPC/E model was also used in this work. Electrostatic interactions were calculated using Smooth Particle Mesh Ewald .…”

“…Detailed knowledge of the solvation properties of electrolytes in aqueous solution is of great importance for understanding chemical and biological processes at the molecular level. − Inorganic CaCl 2 salt plays vital roles in many biochemical processes , and is a major component of the geothermal brines − and energy storage materials. − This great importance has prompted numerous studies on CaCl 2 aqueous solutions, both experimentally − and theoretically, − in recent decades. In the published works, ion-associated characteristics in CaCl 2 aqueous solutions, in particular the contact ion pair (CIP), which was first proposed by Phutela and Pitzer to explain an anomaly in the thermodynamic behavior in near 5.0 mol·kg –1 CaCl 2 aqueous solutions, were generally suspected. ,− The results of Car–Parrinello molecular dynamics (CPMD) simulation by Todorova et al suggested the possibility of ion pairing in 2.0 mol·kg –1 CaCl 2 aqueous solutions, and the work of Rudolph et al using Raman spectra and DFT calculations confirmed the existence of CIPs in concentrated CaCl 2 solutions and hydrate melts.…”

“…The recent work of Jungwirth et al also indicated the formation of ion-associated species in 4.0 mol·kg –1 CaCl 2 aqueous solutions using classical MD simulations, whereas the work of Saxena et al found no CIP structure in 0.1–3.0 mol·kg –1 CaCl 2 electrolyte solutions. The theoretical calculations of Dai et al showed that ion association is not favorable in CaCl 2 aqueous solutions, but CaCl 2 0 was found to be relatively more stable than CaCl + . Ion pairing in CaCl 2 aqueous solutions is therefore a complicated problem.…”

Copper Chloro-Complexes Concentrated Solutions: An Electrochemical Study

“…The (E + + E − )/2 does not change significantly when the chloride concentration increases. In high concentrated solution, calcium chloride is not completely dissociated [35] and theoretical work [36] has shown that Ca 2+ can coordinate chloride to form chlorocomplexes even if the [CaCl x ] 2−x (x = 4-6) clusters become metastable when hydration is considered. The high ionic strength of the solution used implies a low water content for the complete solvation of calcium.…”