Oxygen vacancy formation for transient structures on the CeO2(110) surface at 300 and 750 K.
Ab initio embedded-cluster calculations have been performed for the CeO2(110) surface using temperature induced structures from molecular dynamics (MD) snapshots. As a first step towards understanding how temperature induced distortions of the surface structure influence the surface oxygen reactivity, the energy cost of removing an O atom from the surface was calculated for 41 snapshots from the MD simulation at 300 K. The quantum mechanical embedded-cluster calculations show that already at 300 K the dynamics causes significant fluctuations (root mean square of 0.37 eV) in the O vacancy formation energy (Evac) while the distribution of the two excess electrons associated with the vacancy is virtually unaffected by the surface dynamics and remains localized on the two Ce ions close to the vacancy. It is also found that the quantum mechanical Evac fluctuations can be reproduced by oxygen vacancy calculations using only the relaxed shell-model force field (FF) itself and the MD geometries. Using the FF as the interaction model, the effect of raising the temperature to 750 K and the effect of doping with Ca were investigated for the oxygen vacancy formation.
Herschend
Björn
B
Department of Materials Chemistry, The Angström Laboratory, Uppsala University, Box 538, S-751 21 Uppsala, Sweden.
Baudin
Micael
M
Hermansson
Kersti
K