Relationships among Ionic Lattice Energies, Molecular (Formula Unit) Volumes, and Thermochemical Radii

Abstract

The linear generalized equation described in this paper provides a further dimension to the prediction of lattice potential energies/enthalpies of ionic solids. First, it offers an alternative (and often more direct) approach to the well-established Kapustinskii equation (whose capabilities have also recently been extended by our recent provision of an extended set of thermochemical radii). Second, it makes possible the acquisition of lattice energy estimates for salts which, up until now, except for simple 1:1 salts, could not be considered because of lack of crystal structure data. We have generalized Bartlett's correlation for MX (1:1) salts, between the lattice enthalpy and the inverse cube root of the molecular (formula unit) volume, such as to render it applicable across an extended range of ionic salts for the estimation of lattice potential energies. When new salts are synthesized, acquisition of full crystal structure data is not always possible and powder data provides only minimal structural information-unit cell parameters and the number of molecules per cell. In such cases, lack of information about cation-anion distances prevents use of the Kapustinskii equation to predict the lattice energy of the salt. However, our new equation can be employed even when the latter information is not available. As is demonstrated, the approach can be utilized to predict and rationalize the thermochemistry in topical areas of synthetic inorganic chemistry as well as in emerging areas. This is illustrated by accounting for the failure to prepare diiodinetetrachloroaluminum(III), [I(2)(+)][AlCl(4)(-)] and the instability of triiodinetetrafluoroarsenic(III), [I(3)(+)][AsF(6)(-)]. A series of effective close-packing volumes for a range of ions, which will be of interest to chemists, as measures of relative ionic size and which are of use in making our estimates of lattice energies, is generated from our approach.

Kinetic Stability and Propellant Performance of Green Energetic Materials

“…We have calculated U L for the ammonium salts of anions 1-4 using a relationship [Eq. (13)] developed by Mallouk et al, [61] which was later expanded by Jenkins et al [62] and Gutowski et al [57] U…”

Compositional and structural control on anion sorption capability of layered double hydroxides (LDHs)

“…The thickness of a brucite layer in LDHs is about 2 A [22,311. Given the basal spacing doo3 of 7.7 A for Ni-Al-C03 LDH (Figure I), the interlayer spacing for this material is estimated to be -5.7 A and thus the cage size to be -4.85 A, which can perfectly accommodate a pertechnetate anion of a size of -4.54 A (estimated from ReOi [32]). Either a too large or a too small cage size would tend to destabilize the adsorbed pertechnetate anion.…”

NMR Spectroscopic Evidence for the Intermediacy of XeF3− in XeF2/F− Exchange, Attempted Syntheses and Thermochemistry of XeF3− Salts, and Theoretical Studies of the XeF3− Anion

“…The current study also clarifies inconsistencies that have arisen in recent computational studies relating to the structure of the XeF3 -anion. [25][26][27][28][29] were used in conjunction with known thermodynamic quantities to estimate Hºrxn, Sºrxn, and Gºrxn for eq 1 in the absence of a solvent. The standard enthalpies for the reactions were determined by analyzing their Born-Fajans-Haber cycles (eq 2).…”