Weak H-bond complexes.

The present study focuses on the weak H-bonded (H2O)(n)(HCl)(m) complexes. One of the most recent trends in vibrational spectroscopy has been directed towards intermolecular interactions and motions. A range of spectroscopic techniques including molecular beam electric resonance, pulsed-nozzle Fourier transform microwave, and infrared laser are capable of providing valuable information concerning the structure and properties of a large number of H-bonded complexes. The intermolecular modes can be studied directly by far infrared, low-frequency Raman, and incoherent inelastic neutron scattering spectroscopy. However, the low concentrations of these complexes and interference from the very intense rotational spectra ate occurring in the far-IR regions makes reliable interpretation of the spectra of molecular complexes very difficult task A complete set of intermolecular vibrations has been determinated for only a very limited number of H-complexes. The quantum mechanical ab initio calculations can be of great use in assisting experimentalists with band identifications and elucidation of general principles. Structure, energetics, and vibrational spectrum of row of (H2O)(n)(HCl)(m) complexes were studied in this work. Ab initio calculations were carried out using 6-31G** basis set containing polarization functions on all atoms. Complete optimization of the geometry was performed at the RHF level with the gradient procedures and Newton-Raphson method. The basis set superposition error (BSSE) was calculated(1). The vibrational analysis was done.