IOP PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter 20 (2008) 184021 (19pp) doi:10.1088/0953-8984/20/18/184021 Bridging the temperature and pressure gaps: close-packed transition metal surfaces in an oxygen environment Catherine Stampfl 1 , Aloysius Soon 1 , Simone Piccinin 1 , Hongqing Shi 1 and Hong Zhang 1,2 1 School of Physics, The University of Sydney, Sydney New South Wales 2006, Australia 2 School of Physical Sciences and Technology, Sichuan University, Chengdu 610065, People’s Republic of China E-mail: stampfl@physics.usyd.edu.au Received 31 October 2007, in final form 11 February 2008 Published 17 April 2008 Online at stacks.iop.org/JPhysCM/20/184021 Abstract An understanding of the interaction of atoms and molecules with solid surfaces on the microscopic level is of crucial importance to many, if not most, modern high-tech materials applications. Obtaining such accurate, quantitative information has traditionally been the realm of surface science experiments, carried out under ultra-high vacuum conditions. Over recent years scientists have realized the importance of obtaining such knowledge also under the high pressure and temperature conditions under which many industrial processes take place, e.g. heterogeneous catalysis, since the material under these conditions may be quite different to that under the conditions of typical surface science experiments. Theoretical studies too have been aimed at bridging the so-called pressure and temperature gaps, and great strides have been made in recent years, often in conjunction with experiment. Here we review recent progress in the understanding of the hexagonal close-packed surfaces of late transition and noble metals in an oxygen environment, which is of relevance to many heterogeneous catalytic reactions. In many cases it is found that, on exposure to high oxygen pressures and elevated temperatures, thin oxide-like structures form which may or may not be stable, and which may have little similarity to the bulk oxides, and thus possess unique chemical and physical properties. (Some figures in this article are in colour only in the electronic version) 1. Introduction The interaction of atoms and molecules with surfaces, and the chemical processes which occur thereon, play a critical role in the manufacture and performance of advanced materials which are used in high-tech applications, for example, electronic, magnetic, and optical devices, chemical sensors, heterogeneous catalysts, and hard and corrosion resistant coatings, to name a but few. In particular, the interaction of oxygen with transition metals (TMs) is of high importance for heterogeneous oxidation (and partial oxidation) catalysis (see e.g. [1–3]) and this has motivated large numbers of early studies on oxygen–metal interactions [4–6]. Extending atomic level understanding to elevated temperatures and pressures is highly desirable, and crucial to understanding the function of materials that occur under such conditions, but achieving such knowledge is often not straightforward. For many heterogeneous catalytic reactions, for example, it is now established that the characteristics of a material observed under ultra-high vacuum (UHV) conditions, where classical surface science techniques dominate, can be expected to be different to that under the high temperature and pressure conditions of technical catalysis. In this regime, it is much more problematic to obtain the same level of microscopic information. Nevertheless, there remains a general consensus that the clean metal surface, often assumed to be the catalyst, may not be the active material phase under such conditions. Recently, through experimental and theoretical studies aimed at bridging such gaps, many interesting and significant findings have been reported; e.g., for the carbon monoxide 0953-8984/08/184021+19$30.00 © 2008 IOP Publishing Ltd Printed in the UK 1