Raman Spectra of Liquid MgCl2 and Liquid MgCl2–KCl System

Abstract

Raman spectra of molten MgCl2, MgCl2–KCl, and MgCl2–2KCl were recorded, at 730°, 525°, and 475°C, respectively, using a Cary 81 Raman spectrophotometer. Liquid MgCl2 exhibits three Raman lines with frequencies 269, 214, and 142 cm−1, which are explainable on the basis of the presence of MgCl64— ions with octahedral configuration. Liquid MgCl2–KCl exhibits four Raman lines with frequencies 451, 250, 208, and 158 cm−1; and their polarization characteristics indicate the existence of MgCl3− ions with pyramidal configuration C3v. The Raman spectrum of liquid MgCl2–2KCl is almost similar to that of liquid MgCl2–KCl. Force constants for the various Mg–Cl ionic species were calculated using generalized valence forces.

Structural Analysis of Magnesium Chloride Complexes in Dimethoxyethane Solutions in the Context of Mg Batteries Research

“…Although there is a wave like feature/band in this spectral region, a trustworthy and clear formation of a peak is undeniable. This peak, based on a wealth of previous data, can be confidently associated with Mg–Cl bonds’ vibrations. ,,,,, …”

Elucidating Ionic Correlations Beyond Simple Charge Alternation in Molten MgCl2–KCl Mixtures

“…Using a simple but very effective polarizable ion model that succeeded where other shell-based models or rigid ion models did not, the authors were able to create a generic description of divalent molten salts. A few early Raman spectroscopy studies − are also very important, as they attempted to describe the type of associations and geometries present in the molten states of MgCl 2 and its mixtures with KCl. As will become apparent during the presentation of our X-ray scattering and simulation results, many of the earlier findings and their interpretation still hold valid, but other concepts accepted as facts for decades may need further scrutiny.…”

“…In the early literature on MgCl 2 , − ,,,− significant attention was given to the issue of nearest-neighbor coordination of Mg 2+ . Even then, it was clearly understood that this quantity was ill-defined in the sense that it significantly depended on the criterion used to define the limits of integration for the pair distribution function .…”

MIR, VNIR, NIR, and Raman spectra of magnesium chlorides with six hydration degrees: Implication for Mars and Europa

“…In the Raman spectral range of 1,300-100 cm −1 of six magnesium chloride hydrates (Figure 4c), the peaks around 800 cm −1 are attributed to H 2 O translation (libration), [31,32] the peaks near 600 cm −1 are attributed to hydrogen-bonds from H-O-H [31,32] and the peaks at ≤500 cm −1 could be assigned to Mg─O stretching vibrations and the mode of Mg─Cl. [31][32][33][34][35] For example, the strong peak at 216.8 cm −l belongs to the totally symmetric a lg mode of Mg─Cl and the 136.3 cm −l peak to the e g vibration of Mg─Cl in the Raman spectra of MgCl 2 •6H 2 O. [33,34] The MIR and Raman spectra of the same molecule are generated by different selection rules but are complementary in providing molecular chemical and structural information.…”

“…[31][32][33][34][35] For example, the strong peak at 216.8 cm −l belongs to the totally symmetric a lg mode of Mg─Cl and the 136.3 cm −l peak to the e g vibration of Mg─Cl in the Raman spectra of MgCl 2 •6H 2 O. [33,34] The MIR and Raman spectra of the same molecule are generated by different selection rules but are complementary in providing molecular chemical and structural information. A trend of MIR spectral band-center-shift to low wavenumber following the increase of hydration degree is obvious in the stretching vibrational range (3,800-2,800 cm −1 ) of six hydrates ( Figure 5), which is not clear in bending vibrational range (1,650-1,550 cm −1 ).…”