A QM/MM study of HCl adsorption at ice surface defect sites

The coupled quantum mechanics/molecular mechanics (QM/MM) method was used to study the molecular and dissociative adsorption of HCl at ice surface defect sites. Barrierless dissociation (ionisation) occurs when two dangling surface hydrogen atoms (Hs) provide sufficiently strong solvation of the Cl- product. Solvation of the Cl for the molecularly adsorbed molecules is usually dominated by a single dangling surface H. For the defect sites studied here, the molecular and dissociative adsorption energies are similar to those for adsorption on crystalline ice 1h hexagons (43 and 64 kJ mol(-1), respectively) although the proximity of the solvating Hs to the Cl at the defect site leads to small variations in these energies. (C) 2003 Elsevier B.V. All rights reserved.