Polarizability of the Iodide Ion in Crystal

Abstract

The electronic dipole polarizability of the iodide ion in solid cubic NaI and KI is derived from ab initio electronic structure computations as function of closest cation-anion separation for the four-coordinated zinc blende structure, the 6-fold coordinated rock salt structure, and the 8-fold coordinated phase having the CsCl structure. The contributions from electron correlation were computed using Moller-Plessett perturbation theory taken to the second order. For both NaI and KI, the anion polarizability predicted for the observed rock-salt polymorph at the equilibrium separation agrees well with the value deduced from experiment. The anion polarizabilities increase with both decreasing coordination number at constant distance and with increasing distance at constant coordination number. Both the polarizabilities and their contributions from electron correlation are suppressed in-crystal relative to those computed for the free iodide ion. The ab initio predictions for the derivatives of the anion polarizabilities with respect to closest cation-anion separation are slightly smaller than those deduced from the experimental observations. Reviews of both the latter and the dipole polarizability derivatives previously computed for other alkali halides are presented. The distance dependence of the polarizability of the iodide ion in the point charge representation of the rock-salt lattice, computed ab initio, differs in shape slightly but significantly from that for either NaI or KI. This difference prevents the in-crystal polarizabilities and their distance derivatives from being predicted by shifting the point lattice polarizability function as previously shown to be possible for the salts of the lighter halides. The applicability of the light scattering model description of anion polarizabilities in condensed phases is investigated.

Synthesis, Morphology, and Ion Conduction of Polyphosphazene Ammonium Iodide Ionomers

“…This value agrees with another literature firstprinciples study of iodide electronic polarizability which calculates iodide's α e value to be 9.8 Å 3 , and the ammonium is expected to have a similar value. 43 Therefore, the considerable additional polarizability measured from dielectric spectroscopy and reported by Roberts 42 is proposed to arise from an additional polarization process of the ions occurring at higher frequencies than those measured in our experiments. This polarization process is called atomic or ionic polarization and corresponds to ions having harmonic oscillator like movement relative to each other due to perturbations by the applied electric field.…”

van der Waals interactions in DFT using Wannier functions without empirical parameters

“…44 It is also close to the "best estimate" (obtained from a combination of experimental and theoretical, mainly semiempirically-based, data) reported in the milestone review paper by Vidali et al, 45 that is -99 ± 4 meV. Our DFT/vdW-WF2-x(PBE) computed Ar-graphite equilibrium distance is instead somehow larger than that reported in other theoretical studies 42,43 (3.3Å), and also than the "best estimate" by Vidali et al 45 of 3.1 ± 0.1Å (and an old experimental measurement of 3.2 ± 0.1Å, see ref. 45).…”

Halogen-bond mediated efficient storage of extremely volatile perfluoroiodides in ionic liquids

“…These chemical shift changes are significantly high indicating the strong halogen bonding interactions between iodide anion in both ionic liquids and the perfluoroiodide. Higher polarisability of the iodide, 16 hence, its ability to donate electrons easily towards more electrophilic centres is well documented and probably, accounts for its ability to form stronger halogen bonds. Armed with these initial findings, we carried out a comprehensive 19 F nmr study with a broad range of ionic liquids carrying a diverse collection of anions.…”