A theoretical study of HArF, a newly observed neutral argon compound

Computational results up to the CCSD(T)/aug-cc-pV5Z level are presented as support for the newly observed argon containing compound, hydrido argonfluoride (HArF). The molecule is calculated to be linear with R(H–Ar)=132.9 pm and R(Ar–F)=196.9 pm. The calculated vibrational frequencies, corrected for anharmonicity and matrix effects, are 462 (Ar–F stretch), 686 (bend) and 1916 cm−1 (Ar–H stretch). These are in good agreement with the corresponding experimentally observed frequencies of 435.7, 687.0, and 1969.5 cm−1 for the matrix isolated species [Nature 406, 874 (2000)]. Including corrections for the finite basis set as well as for the zero-point energy, the new molecule is stable by 0.15 eV compared to the dissociated atoms. HArF is further stabilized by an additional barrier of 0.18 eV, arising from the avoided crossing between the states corresponding to the ionic (HArδ+)(Fδ−) equilibrium structure and the covalent (HAr⋅)(F⋅) dissociation limit. The dissociation of HArF via bending into the thermodynamic ground-state system, consisting of Ar and HF, is protected by a 1.0 eV barrier.