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Atomistic Simulation Group, School of Mathematics and Physics,
Queen's University, Belfast BT7 1NN, U.K.
School of Chemistry, Queen's University, Belfast BT9 5AG, U.K.
Ali Alavi , Peijun Hu
November 16, 1998
CO oxidation on Pt(111) is studied with ab initio
density functional theory, using plane-waves and pseudopotentials.
The low energy pathway and transition state
for the reaction CO/ 
-O/Pt(111) 
CO 
/Pt(111) are identified using a constrained
minimisation scheme. ( Snaphots of the reaction pathway can be downloaded
from
.
See also [1]).
The transition state consists of the O atom
at a bridge site, and the CO molecule at a neighbouring top site,
with C-O separation of 2.1Å. The activation energy 
eV.
Approximately 60% of this energy can be accounted for by
the O atom moving from the hollow to bridge site ( thereby breaking
a O-metal bond), while the remainder is due mainly to placing
a CO atom at a top site adjacent to the bridging O atom. The
pathway can be rationalised in terms of competition of the O and C atoms
for bonding with the underlying surface. It is suggested
that the physical origin of the predominant barrier is the strength of the O-metal bond,
and modification of this bond strength can be expected to
affect crucially the catalytic activity.