A theoretical study of gas-phase and solid-state Hg(CF3)2

Gas-phase and solid-state Hg(CF3)2 have been studied using a relativistic density-functional method. The crystalline environment was simulated by a cut-off-type Madelung potential. Bond lengths, dissociation energies, force constants, and enthalpy of sublimation are calculated. The influence of the crystal field (CF) on the molecular properties is well reproduced by the CF model. The intermolecular bonding in the crystal structure is examined and is revealed to be dominated by electrostatic effects. The relatively high enthalpy of sublimation evaluated for the crystal compound (ΔHsub=18.7 kcal) accounts for its relatively high melting points. A hypothetical crystal Hg(CH3)2 is shown to have a small ΔHsub (3 kcal mol−1), which explains why no solid-state Hg(CH3)2 exists. Ionization potentials for all the valence MOs of the gas-phase Hg(CF3)2 are predicted.