Universal Parameter for the Extrapolation of Force Constants, Mean-Square Quantities, and Bond Energies of Halides

Abstract

A general formula of the type Y = kω + C, which is simultaneously applicable to force constants, the reciprocals of the mean-square amplitude quantities σr, bond dissociation as well as thermochemical bond energies of halides, has been presented. ω, moreover, is given by the expression ω = 16 | χm − χx | + 3.5(χm − χx)2 + θf, where χm and χx are the Pauling electronegativities of the atoms forming the M–X bond, and where θf is a constant for each of the aformentioned molecular parameters and may have a nonzero value only in the fluorides. The θf values for the three parameters studied were found to be 0, − 11, and − 15 or − 30, respectively. The choice of the latter depends on whether χm > 1 (− 15), or χm ≤ 1(− 30), except for the NaX series for which θf = − 15.