Vibrational frequencies and geometries for the open HF trimer

Abstract

Non-cyclic structures of the HF trimer are investigated using self-consistent-field (SCF) wavefunctions constructed from basis sets of double-zeta (DZ) and double-zeta plus polarization (DZ+P) quality. Cis and trans planar stationary points for the open trimer were found with the DZ SCF method, corresponding to a minimum and a transition state, respectively. With the DZP SCF method the trans structure is again a transition state but we were unable to locate an analogous cis stationary point. Thus we find little evidence for the existence of any conformational minimum of the HF trimer other than the cyclic structure. Vibrational frequencies and infrared intensities were predicted from analytic energy and dipole moment derivatives at the SCF level of theory. Predicted values for the vibrational frequency shifts relative to the HF monomer are also given and compared with experimental results.