Ab Initio Monte Carlo Simulated Annealing Study of HCl(H₂O)_n (n = 3, 4) Clusters

Abstract

Low-lying structures of HCl (H2O) n (n = 3, 4) clusters have been studied by ab initio Monte Carlo simulated annealing (MCSA), a procedure which efficiently samples minima on a potential energy surface. In the Monte Carlo simulated annealing procedure, energies were computed ab initio at each Monte Carlo step by the B3-LYP density functional method with 6-31G* basis sets. All geometries of the isomers found for each cluster were refined in full conventional geometry optimizations, and frequency analyses were performed at both the B3-LYP and MP2 levels with 6-311+G** basis sets. The stability of the B3-LYP and MP2 energy orderings was tested in single point QCISD(T) calculations performed at the MP2 optimized geometries. Only isomers with strong H−Cl interaction were found for HCl(H2O)3. However, both associated- and dissociated-HCl structures of HCl(H2O)4 were found.

Structural properties of nanoclusters: Energetic, thermodynamic, and kinetic effects

“…Solov'yov et al (2003a,b) applied this method to LJ clusters, starting from a tetrahedron, and adding one atom at a time according to different procedures (adding an atom on the surface, inside the surface, or at the center of mass of Seifert (1992), Stave and DePristo (1992), Cheng et al (1993), Jones (1993), Christensen and Cohen (1993), Ma and Straub (1994), Bacelo et al (1999), Ahlrichs and Elliott (1999). the cluster).…”

Fragmentation of HCl–water clusters upon ionization: Non-adiabatic ab initio dynamics study

“…One of the fundamental questions of cluster chemistry is the cluster size at which the acidic dissociation occurs [6][7][8][9][10][11][12][13]. Typically 4-6 water molecules are reported to enable the acidic dissociation.…”

Infrared Spectroscopy of (HCl)m(H2O)n Clusters in Helium Nanodroplets: Definitive Assignments in the HCl Stretch Region

“…[15][16][17][18][19][20][21][22][23][24][25] These ab initio studies generally agree that four water molecules are necessary before the ion pair becomes the minimum energy structure. 16,17,19,20,26,27 On the experimental front, microwave [27][28][29][30] and cavity ring-down infrared 31 spectroscopy have provided structural data for some of the smaller, undissociated (HCl) m (H 2 O) n clusters, such as the 1:1 and 1:2 complexes. Fourier transform infrared (FTIR) spectroscopy of these clusters grown in solid matrices [32][33][34][35] or formed in free-jet expansions 24,36 have provided overview spectra in the OH and HCl stretch regions.…”