Chemical bonding in XeF2, XeF4, KrF2, KrF4, RnF2, XeCl2, and XeBr2: From the gas phase to the solid state

This paper presents a systematic investigation of chemical bonding in a ser ies of noble-gas halides in both the gas phase and the solid state. The cry stalline environment was simulated by a cutoff type Madelung potential. Geo metries, dissociation energies, force constants, and enthalpies of formatio n and of sublimation were determined. The calculated properties are in good agreement with available experimental data. The crystal field model is cap able of reproducing all significant differences observed between the gas ph ase and the solid state. KrF4, XeCl2 and XeBr2 are predicted to be rather u nstable against molecular dissociation. The stabilities of the dihalides fo llow the order KrF2 much less than XeF2 < RnF2 and XeF2 much greater than X eCl2 approximate to XeBr2. The calculated trends account for the fact that only the heavier noble gases form compounds and that the electronegativity of the ligand has to be large. The outer polarization orbitals play an impo rtant role in the bonding. Relativistic effects on the molecular properties are negligible.