A Refined Ionic Model for Clusters Relevant to Molten Chloroaluminates

Abstract

A model of ionic interactions in neutral and ionized aluminium trichloride clusters, which accounts for ionic deformability through (i) effective valences and (ii) electrostatic and overlap polarizabilities, is evaluated for applications to classical simulation studies of the pure melt and of molten alkali chloroaluminates. The disposable parameters in the model are determined from the measured values of the bond length in the (A1C1 4 )~ molecular ion and of an Al-Cl bond length and a vibrational frequency in the A1 2 C1 6 molecular dimer. The model is tested against the remaining available data from experiment and from quantum chemical calculations on molecular bond lengths, bond angles and vibrational frequencies for A1 2 C1 6 , (A1C1 4 )~ and (A1 2 C1 7 )~ clusters. Structural and dynamical properties are also evaluated for the (A1 2 C1 5 ) + , A1C1 3 and (A1C1 2 ) + clusters. The results for the energetics of dissociation, ion transfer and isomer excitation reactions are compared with as yet unpublished data obtained by P. Ballone in first-principles calculations by a density functional method. The overall quality of the tests supports the approximate validity and transferability of the model.

An Aluminum–Sulfur Battery with a Fast Kinetic Response

“…In the EMICl/AlCl 3 electrolyte, an isolated Al 2 Cl 7 − anion consists of two AlCl 4 tetrahedra sharing a Cl atom in a bent configuration with two Al−Cl bonds denoted as Al−Cl T and Al−Cl B , respectively (shown in Figure a). The longer Al−Cl B bond length (2.35 Å vs. 2.10 Å) implies that the dissociation of an Al 2 Cl 7 − anion should start by breaking the Al−Cl B bond first. Therefore, the strength of this bridge bond determines the dissociation reaction rate of the Al 2 Cl 7 − anion.…”

A Polarizable-Ion Potential for Trihalides: from Clusters to Liquid Structure

“…Full explicit expressions of the potential energy function and the halogen dipoles for an arbitrary configuration of the ionic assembly can be found in Ref. (10). As already noted, the values of the various force-law parameters for the liquids of present interest have been taken from Ref.…”

A High‐Performance Na–Al Battery Based on Reversible NaAlCl4 Catholyte

“…It is well known that Al 2 Cl 7 − anion consists of two tetrahedrally coordinated Al atoms bridged by a chlorine atom in a bent configuration. [ 12 ] The longer AlCl bond length of the AlClAl bridging bond (2.35 Å vs 2.15 Å of tetrahedrally coordinated AlCl bond) allows easier breakage of the AlClAl bond, [ 12,13 ] leading to a favorable Al redox reaction as follows: [ 5,9a,b,14 ] …”

“…; unfortunately, the reversible Al platting/stripping is generally prohibited in NaAlCl 4 at room temperature, because of its excellent chemical stability originated from its tetrahedral shape (AlCl bond length is 2.15 Å and ClAlCl angle is 109.5°). [12] Therefore, AlCl 4 − anion has been widely used as a stable counter-anion for other metal battery electrolytes, such as magnesium electrolytes. [15] However, a reversible Al deposition from NaAlCl 4 is not entirely impossible especially at elevated temperatures above its melting point (157 °C) where it is in molten state.…”