Chemistry Reference
In-Depth Information
Chapter 6
Water Clusters: Formation
of One-Dimensional Water Clusters
Abstract I describe the assembly and characterization of small water clusters on a
Cu(110) surface in this chapter. One-dimensional (1-D) chain-like clusters (3-6
molecules), where water molecules are arranged along the Cu row to form a
''ferroelectric'' zigzag configuration, are assembled in a fully controlled fashion
using the STM manipulation. H-bond rearrangements in the clusters are induced
by a voltage pulse of STM. In addition to the chain configuration, several structural
isomers are observed in larger clusters than tetramer. DFT calculations suggest a
chain configuration is preferred for trimer in spite of the reduced number of
H bond, while a cyclic configuration in which the number of H-bond is maximized
becomes more favorable for tetramer, indicating the crossover of the stability from
a chain to cyclic configuration.
Keywords Small water clusters
H-bond rearrangement
STM manipulation
6.1 Introduction
A water cluster is a discrete H-bonded assembly of water, which is of particular
interest to understanding anomalous water characteristics. Water clusters are
considered as a model system to examine the many-body, or cooperative nature of
H-bonding interaction. Terahertz laser vibration-rotation-tunneling and mid-IR
spectroscopy have been employed to observe small water clusters (2-6 molecules)
[
1
]. Numerous semi-empirical and ab initio quantum mechanical calculations on
water clusters have also been reported [
2
]. For trimer to pentamer, it was found to
form a cyclic structure where each monomer acts both as a single donor and
acceptor of H-bond.
The structure and growth mechanism of water clusters on metal surfaces are
related to various chemical processes such as wetting, corrosion, and heterogeneous
