The stabilities of the hydrogen fluoride trimer and tetramer

Abstract

A b initio calculations have been carried out to determine the dissociation pathways for the hydrogen fluoride trimer and tetramer that are accessible with single photon excitation of an HF stretching vibration. This requires evaluation of the stabilities of the small HF clusters. Electron correlation effects are found to contribute 1.0 kcal to the stability of the trimer, compared to 0.5 kcal for the dimer. The equilibrium stabilities with respect to dissociation into monomers are 4.6 kcal for the dimer, 14 kcal for the trimer, and 25 kcal for the tetramer. With zero-point vibrational effects, single photon vibrational excitation is sufficient for dissociation of the trimer into three monomers. The orientational structural parameters of the trimer and tetramer, like those of the dimer are found to be well explained by dipole and quadrupole moment interactions.