6th International Conference on Aperiodic Crystals (APERIODIC'09)

Aperiodic'09, the sixth International Conference on Aperiodic Crystals, took place in Liverpool 13–18 September 2009. It was the first major conference in this interdisciplinary research field held in the UK. The conference, which was organised under the auspices of the Commission on Aperiodic Crystals of the International Union of Crystallography (IUCr), followed on from Aperiodic'94 (Les Diablerets, Switzerland), Aperiodic'97 (Alpe d'Huez, France), Aperiodic'2000 (Nijmegen, The Netherlands), Aperiodic'03 (Belo Horizonte, Brazil) and Aperiodic'06 (Zao, Japan). The next conference in the series will take place in Australia in 2012. The Aperiodic conference series is itself the successor to a series of Conferences on Modulated Structures, Polytypes and Quasicrystals (MOSPOQ), which were held in Marseilles (France) in 1984, Wroclaw (Poland) in 1986, Varanasi (India) in 1988 and Balatonszeplak (Hungary) in 1991. The remit of the conference covers two broad areas of research on aperiodic crystals, incommensurately modulated and composite crystals on the one hand, and quasicrystals on the other hand, sharing the property that they are aperiodically ordered solids. In addition, the conference also featured recent research on complex metal alloys, which are in fact periodically ordered solids. However, the term complex refers to their large unit cells, which may contain thousands of atoms, and as a consequence complex metal alloys share some of the properties of quasicrystalline solids. Aperiodic'09 attracted about 110 participants from across the world, including 20 UK-based scientists (the second largest group after Japan who sent 21 delegates). A particular feature of the conference series is its interdisciplinary character, and once again the range of disciplines of participants included mathematics, physics, crystallography and materials science. The programme started with three tutorial lectures on Sunday afternoon, presenting introductory overviews on quasicrystals (Eiji Abe), complex metal alloys (Alessandra Beni) and incommensurately modulated structures (Gervais Chapuis). While these were mainly aimed at younger researchers in the field, the lectures were very well attended and appreciated by the participants. The main programme ran from Monday morning until Friday lunchtime. It comprised 13 invited and 40 contributed plenary talks, and more than 40 posters, which were presented at two afternoon/evening poster sessions. The topics covered in the programme range from mathematical foundations, mathematical models, new materials, sample preparation, structure determination, physical properties and surface properties to industrial applications. Every presenter was invited to submit an article for this proceedings volume, and the 36 peer-reviewed papers in this volume present a cross-section of the range of presentations at the conference. They have been arranged into four categories, (i) quasicrystals, (ii) modulated structures, (iii) mathematical and theoretical aspects of aperiodic order, and (iv) approximants and complex phases. Prizes for best student presentations were awarded to Heinrich Orsini-Rosenberg (ETH Zurich) for his poster Tailor-made sevenfold approximants: ab-initio investigations on formation and stability and to Holger Euchner (Universitat Stuttgart) for his contributed talk on Lattice dynamics in complex metallic alloys – vibrational properties of Zn11Mg2. In addition to a cash prize, Heinrich Orsini-Rosenberg received an icosahedral teapot, which was manufactured and donated by David Warrington, and Holger Euchner received a book prize. The meeting started with a welcome reception in the University's recently refurbished Victoria Gallery and Museum. A public lecture Simple sets of shapes that tile the plane but cannot ever repeat by Professor Sir Roger Penrose FRS attracted a wide audience and gave a fascinating insight into the discovery of the Penrose tiling, which is still the paradigm of aperiodic order in two dimensions and used in modelling quasicrystalline materials, some ten years before quasicrystals were first seen in experiment. The conference excursion and dinner centred on the historic waterfront area of this 800-year old city that was designated European Capital of Culture in 2008. The enjoyment of the ferry trip on the Mersey and subsequent walk to the Albert dock museums was greatly enhanced by the fine weather, which lasted throughout the entire conference week. The guests of honour at the conference dinner were Professor Sir Roger Penrose FRS and Professor Alan L Mackay FRS, bringing together two distinguished UK scientists who made seminal contributions to the subject. Besides the scientific programme, the conference also offered a presentation by the author Ann Lingard, whose latest novel The Embalmer's Book of Recipes features a mathematician working on quasicrystals at the University of Liverpool as its main character. A related EPSRC-supported workshop on Mathematical Aspects of Aperiodic Order, organised by Alex Clark, John Hunton and Uwe Grimm, was held in Leicester in the week preceding the conference, and attracted about 40 participants. It is not possible to organise a conference without the help and support of a large number of people, and we would like to take this opportunity to acknowledge the support of everyone who was involved in organising and running this conference. We would like to thank the IUCr Aperiodic Commission, and in particular its chair Professor Marc de Boissieu, who not only entrusted us with hosting the event, but acted as the International Advisory Committee and provided valuable advice and guidance. We are indebted to the members of the International Programme Committee, who helped to put together an exciting programme by suggesting invited speakers and selecting presentations for contributed plenary talks. We are immensely grateful to all members of the National Organising Committee, who provided essential support during the organising stage and during the conference itself, and we would particularly like to thank the conference secretary, Mrs Angie Reid, for her excellent administrative support before, during and after the conference, and for her help in the production of this volume. We are very much indebted to out co-editors, Dr Olga Degtyareva (Edinburgh) and Dr Hem Raj Sharma (Liverpool), for their contributions to the editing of this volume. Finally, and most of all, we would like to thank all participants of the conference for coming to Liverpool, for contributing by presenting their recent work and taking part in discussions, and for creating such an enjoyable and fruitful collegiate atmosphere throughout the week. Last but not least we would like to express our gratitude for the generous financial support we received from the Open University, the University of Liverpool and the Institute of Physics (Mathematical and Theoretical Physics Group and Thin Films and Surfaces Group). The International Union of Crystallography provided financial sponsorship which was allocated to support the participation of 15 young scientists. The European Network of Excellence on Complex Metallic Alloys provided travel and subsistence support to members of participating organisations. Ronan McGrath Uwe Grimm