T.P. Pearl, NCSU

1
T.P. Pearl, NCSU
Scanning Tunneling Microscopy (STM) is ideally
suited as a probe for the identification of
intermediates and reaction sites in surface
chemical reactions via the imaging of the surface
structure and of the reaction products. STM alone
however can distinguish between different surface
patterns but cannot give us a real space image of
the atomic configuration that corresponds to a
given stage of any reaction process. For this
reason, simulations of the true electronic
structure of the system are indispensable for a
complete understanding of the experimentally
recorded images.
Comparison between an experimental and a
theoretical STM image of a graphite sheet, the
catalytic substrate for the water dissociation
reaction that has been the subject of the REU
work. In the inset, the STM of the Lab of T.P.
Pearl ant NCSU.
2
The REU undergraduate student Kara Beharry, has
simulated the STM images that correspond to the
various stages of the water dissociation reaction
on a vacancy in a graphite surface, and has
identified the peculiar features of the
individual intermediate states. Her results will
help understand the experimental measurements
that are underway at NCSU and will be of
relevance in view of the worldwide effort in the
search for an alternative and energy efficient
method of hydrogen production.
An oxygen atom from the dissociated water
molecule sits on the graphite sheet to saturate a
vacancy site. Computationally it can be shown
that the STM image reveals the bonding pattern
around the oxygen atom.
The two hydrogen atoms saturate one carbon atom,
while the oxygen atom bridges the remaining
carbons in one of the intermediate states of the
dissociation reaction.
Phys. Rev. Lett. (2005), in press