Electron Correlation and the Reality of Xenon Difluoride

Abstract

The electronic structure of xenon difluoride has been studied using ab initio theoretical methods. The primary goal was to determine whether current theoretical methods are capable of yielding a reasonable value of the dissociation energy of XeF2. A Slater function basis set of slightly better than “double ζ plus polarization” quality was employed. Four different types of wave functions were investigated: two-configuration SCF, full valence configuration interaction (Cl), the first-order wave function, and a larger 1234 configuration wave function including all double excitation from the 10σg orbital. Although the TCSCF symmetric stretching potential curve has both a minimum and maximum, the minimum lies above the comparable energy of separated Xe + 2F. However, the two most complete wave functions predict dissociation energies of 1.97 and 2.14 eV, in qualitative agreement with experiment, 2.78 eV. All four wave functions provide good predictions of the Xe-F equilibrium bond distance. As was the case for KrF2, the bonding in XeF2 is found to conform quite closely to Coulson's model F Xe+ F- ↔ F- Xe+ F near the equilibrium geometry. The role of the “outer orbitals” 5d and 4f appears to be a quantitative rather than qualitative one. © 1975, American Chemical Society. All rights reserved.