Relativistic ab initio and density functional theory calculations on the mercury fluorides: Is HgF_4 thermodynamically stable?

摘要

Structural and energetic properties of the experimentally yet unknown gas-phase molecule mercury(IV) fluoride HgF_4 have been calculated with three independent quantum-chemical approaches accounting for relativistic and electron correlation effects. All-electron 4-component density functional and scalar relativistic direct perturbation theory as well as valence-only quasi-relativistic pseudopotential calculations predict HgF_4 to be thermodynamically stable by at least 19 kJ/mol with respect to HgF_2 and F_2, and by at least 690 kJ/mol with respect to atomization. The Hg-F bond length and the totally symmetric Hg-F stretching mode are predicted to be 1.910 +- 0.015 A and 565 +- 25 cm~(-1), respectively. HgCl_4 is predicted to be unstable with respect to HgCl_2 and Cl_2. The ionization potentials and excitation energies of the Hg atom and its cations are presented.