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The structure and spectroscopy of monolayers of water on MgO: An ab initio study

Summary: The structure and spectroscopy of monolayers of water on MgO:
An ab initio study
L. Delle Site,a)
A. Alavi, and R. M. Lynden-Bellb)
Atomistic Simulation Group, School of Mathematics and Physics, The Queen's University, Belfast BT7 1NN,
United Kingdom
Received 10 April 2000; accepted 31 May 2000
The structure and energetics of a monolayer of water on a perfect MgO substrate is investigated by
ab initio calculations. Several minima in the potential energy surface were found including both
physisorbed and chemisorbed states in which one third of the water molecules were dissociated. In
the more stable of the physisorbed states, the water molecules were not all parallel to the surface,
but some showed hydrogen bonding with surface oxygen ions. Even in the physisorbed state, the
geometry of these surface H-bonded water molecules were distorted relative to the bulk. One of the
stable chemisorbed states was the same as that found in earlier work by Giordano et al. Phys. Rev.
Lett. 81, 1271 1998 . Two more stable chemisorbed structures were found in which strong
hydrogen bonds to the hydroxide ions in the water layer were formed. The existence of different
minima appears to be the result of a subtle interplay between hydrogen bonding between adsorbed
species and with the surface oxide ions. Harmonic vibrational frequencies were determined for both
a chemisorbed and a physisorbed states and spectroscopic features which should discriminate
between chemisorbed and physisorbed states are identified. 2000 American Institute of Physics.


Source: Alavi, Ali - Department of Chemistry, University of Cambridge


Collections: Chemistry