Ab initio studies on clusters of polar molecules. stability of cyclic versus open-chain trimers of hydrogen fluoride

Large-scale ab initio calculations have been performed on cyclic and open-chain trimers of hydrogen fluoride including partial geometry optimization. The cyclic trimer turned out to be more stable by ≈ 2 kcal/mole. Equilibrium geometries and hydrogen bond energies are compared with corresponding quantities of (HF)₂ and of the infinite chain (HF)∞.