Ab initio studies on hydrogen-bonded trimers: structure and vibrational spectra of HCN(HF) 2 and (HCN) 2HF

Abstract

Equilibrium structures and vibrational spectra of HCN(HF) 2 and (HCN) 2HF were investigated with the aid of ab initio methods by applying extended basis sets and including electron correlation at a size-extensive level. We compare the computed ground-state properties such as the equilibrium structure, stabilization energy, dipole moment, vibrational spectra and infrared intensities of the trimers with those of the HF and HCN monomers, with the (HF) 2, HCN-HF and (HCN) 2 dimers and with the available experimental data. Modifications to the monomer properties induced by cluster formation are discussed. The computed trimer structures are in good agreement with recent vapour-phase data and may be rationalized as a superposition of the constituent dimer structures.