Theoretical study of the protolytic dissociation of HCl in water clusters

Abstract

Reaction mechanisms for the acidic dissociation of HCl in water clusters are considered. Intermediates in the reaction are obtained from stationary points on the potential energy surface of the systems HCl-͑H 2 O͒ n with nϭ4 and 5. These points have been determined by the B3LYP density functional method in an aug-cc-pVDZ atomic orbital ͑AO͒ basis. The total energies of the stationary points are checked by the coupled cluster single-double-triple ͓CCSD͑T͔͒ method in the same AO basis. For the case of nϭ4 a multibody analysis of the interaction energies is performed by the CCSD͑T͒ method as well as by symmetry adapted perturbation theory. The clusters have a completely dissociated form as their energetically lowest minimum.

Finite-Temperature Effects on the Stability and Infrared Spectra of HCl(H2O)6 Clusters

“…19 Using the B3LYP density functional method and the CCSD(T) ab initio method, Milet et al showed however that HCl starts dissociating already in HCl(H 2 O) 4 . 20 Devlin et al, using ab initio Monte Carlo simulations found that in HCl-(H 2 O) 6 three-coordinated HCl dissociates directly to form a clearly recognizable solvated Cl -and H 3 O + ion pair. 21 They also suggested that to induce ionization, HCl must bind to a two-coordinated dangling-O molecule, that is, one that does not accept a proton from another H 2 O molecule.…”

Electric Dipole Moments of Nanosolvated Acid Molecules in Water Clusters

“…One inquiry that persistently threads its way through this subject is: what is the minimum quantity of water molecules, (H 2 O) n , required to dissociate the acid [18]? According to calculations, the acidically dissociated structure is supported starting from n=4; most of the theoretical approaches agree that at this size the dissociated form represents the global minimum on the potential energy surface [18][19][20][21][22][23][24]. Experimentally, for neutral clusters the question has been probed by laser spectroscopy (see, e.g., [25][26][27][28]) but finding a conclusive spectroscopic signature of the onset of dissociation in a nanocluster is not straightforward.…”

Ab initio prediction of the vibration-rotation-tunneling spectrum of HCl–(H2O)2

“…Even more than in the water trimer, the three-body effects are considerable 66 in the very polar system HCl-͑H 2 O͒ 2 . Consequently, the results of a study on the trimer will be useful for larger clusters, as the most important interactions, the pair-and the three-body interactions, are present in the trimer.…”