Physica B 318 (2002) 211–216 Oxygen adatom diffusion on the NiO(0 0 1) surface by molecular dynamics simulation D.G. Papageorgiou a , T. Karakasidis b,c , G.A. Evangelakis d, * a Department of Materials Science, University of Ioannina, 45110 Ioannina, Greece b Department of Civil Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece c Department of Computer Engineering, Telecommunications, and Networks, Argonafton & Filellinon, 38221 Volos, Greece d Department of Physics, Solid State Division, University of Ioannina, P.O. Box 1186, 45110 GR Ioannina, Greece Received 8 November 2001 Abstract We present results concerning the diffusion processes of O 2 adatom on the NiO(0 0 1) surface obtained by molecular dynamics simulations based on a rigid ion potential model. We covered a temperature region from 0:37T m up to 0:71T m ; T m being the melting point of the model system. It came out that the energetically favoured adatom position is located at the hollow site of the Ni sublattice. From the detailed analysis of the ionic trajectories, we found that the adatom diffuses via simple hopping and multiple exchange mechanisms. All processes exhibit Arrhenius behaviour from where we deduced the corresponding migration energies. Moreover, we found that although the frequency rates for hopping and exchange are comparable, the participation of the latter to the total diffusion coefficient is more important than that of hopping, by as much as an order of magnitude at high temperatures. r 2002 Elsevier Science B.V. All rights reserved. PACS: 66.10.Ed; 66.30.Hs; 81.05.Je; 82.20.Wt Keywords: Diffusion; Oxides; Adatoms; Molecular dynamics 1. Introduction Oxygen adsorption on oxide surfaces is related to many technologically important applications such as photo-voltaic devices, coatings for corro- sion passivation, gas sensors and oxide-supported transition metal catalysts, crystal growth [1–4], etc. The oxygen adatom behaviour is therefore of fundamental importance in the understanding of the various processes happening on the surfaces. The adatom equilibrium positions on the surface, along with their diffusive behaviour, are among the decisive quantities involved in the first stages of interface formation or the development of over- layers on oxide surfaces [1,5,6]. Experimentally, various techniques like ultra- violet and X-ray photoemission, Auger spectro- scopies and low-energy-electron diffraction [7] have been used to obtain the electronic struc- ture of surface defects on NiO(1 0 0) and their *Corresponding author. Tel.: +30-651-98590; fax: +30-651- 45631. E-mail address: gevagel@cc.uoi.gr (G.A. Evangelakis). 0921-4526/02/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0921-4526(02)00517-3