BEYOND QUASICRYSTALS Les Houches, March 7-18, 1994 Editors Fran~oise Axel, Universire Paris VII-Denis Diderot Denis Gratias, CECN-CNRS, Vitry Springer-Verlag Berlin Heidelberg GmbH ISBN 978-3-540-59251-8 ISBN 978-3-662-03130-8 (eBook) DOI 10.1007/978-3-662-03130-8 This work is subject to copyright. AlI rights are reserved, whether the whole or part of the material is concemed, specificalIy the rights of translation, reprinting, re-use of illustrations, recitation, broad-casting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted under the provisions of the French and German Copyright laws of March lI, 1957 and September 9, 1965, respectively. Violations falI under the prosecution act of the French and German Copyright Laws. © Springer-Verlag Berlin Heidelberg 1995 Originally published by Springer-Verlag Berlin Heidelberg New York in 1995 The school was supported by: Universite Joseph Fourier de Grenoble Centre National de la Recherche Scientifique (CNRS-fonnation pennanente) Direction des Recherches et Etudes Techniques (DGA-DRET) xn Commission of the European Communities -DG Minisrere des Affaires Etrangeres Obituary Professor Gerhard Fritsch, who lectured in our School "Beyond Quasicrystals" on transport properties in quasiperiodic media, died suddenly and unexpectedly on April 14, 1994. Gerhard Fritsch was born on July 3, 1940 in Marktredwitz in Nothern Bavaria where he also spent his school time. Afterwards he studied physics at the Technical University (TU) of Munich and got there his PhD in 1969 with a work on "Measurements on the thermic and electric conductivity of sodium directly at the melting point". From 1969 to 1975 he worked as Scientific Research Assistant at the Physics Department of the TU Munich. From 1975 to 1977 he was Research Associate at the University of lllinois (USA). In 1977 Gerhard Fritsch was appointed as a Senior Research Scientist at the Physics Department of the TU Munich and became in 1979 full Professor for Experimental Physics at the University of the Armed Forces Munich. In 1984 he spent a year at the University of California at Los Angeles (USA). Besides the stimulating work in his Institute Professor Fritsch was committed to the development of the knowledge in modem physics for teachers. He served as co-editor of the German journal "Physik in unserer Zeit" for more than two decades. In research, he combined interests for fundamental topics as the transport properties of amorphous and quasi crystalline alloys or the determination of the diffuse X-ray scattering of sodium with interests for more applied studies as measurements of the properties of materials by means of micro beam X-rays. To his wife, who was with him in Les Houches and to their young daughter, we present the expression of our heartfelt sympathy. Foreword This book is the collection of most of the written versions of the Courses given at the Winter School "Beyond Quasicrystals" in Les Houches (March 7-18, 1994). The School gathered lecturers and participants from all over the world and was prepared in the spirit of a general effort to promote theoretical and experimental interdisciplinary communication between mathematicians, theoretical and experimental physicists on the topic of the nature of geometric order in solids beyond standard periodicity and quasi periodicity. The overall structure of the book reflects the wish of the editors to pose this fundamental question of geometric order in solids from both the experimental and theoretical point of view. The first part is devoted more specifically to quasicrystals. These materials were the common starting point of most of the audience and present a first concrete example of a non-trivial geometric order. We chose to focus on a few fundamental aspects of quasicrystals related to hidden symmetries in solids which are not easily found in standard textbooks on the topic, not to reach an exhaustive survey which is already available elsewhere. Y. Meyer redevelops here a few of the ideas presented in his 1972 book "Number theory and harmonic analysis". It is a unique occasion for most physicists of the quasicrystal community to discover Y. Meyer's very early synthetic definition of a "quasicrystal". Basics of geometry, structural and dynamical properties of quasicrystals are given by T. Janssen, whereas the more experimental crystallographic aspects are developed by W. Steurer and P. Mikulic. "Special" symmetries in quasicrystals form the basis of the lectures by J. Patera, P. Kramer and A. Janner, respectively on "Pentacrystals", on non commutative geometry, the other on multimetrical analysis. All three extend the field of crystallography by introducing more general concepts than simple isometries. The fundamental question of understanding the propagation of non trivial order by local interaction "matching rules" in quasi crystals is discussed by A. Katz in connection with the problem of atomic diffusion by P. Kalugin. Defects in aperiodic materials from quasicrystals to amorphous are presented and compared by N. Rivier. The second part deals with deterministic aperiodic order "beyond" quasip eriodicity. Deterministic sequences are a major example of quasicrystal generalization. Different properties are presented here from basics in the VI Courses by M. Mendes France and J.-P. Allouche, to automatic walks by M. Dekking with possible relationships to diffusion. Their Fourier transforms are discussed in great details by M. Queffelec based on the general notions of measures and substitution dynamical systems. V. Berthe presents and discusses their entropies, Z. Y. Wen the subwords appearing in the Fibonacci substitution and its generalizations. Algebraic properties appear in the Course on trace maps by J. Peyriere. Realizations in physics of such deterministic aperiodic sequences are at present of two kinds - SchrOdinger type equations having such a deterministic sequence for a potential. This very important topic is presented in the Courses by A. Siito and H. Kunz. - Multilayers systems which are now being studied mostly by diffractionnists Finally, an introductory Course with basics for multifractal analysis is given by J. Peyriere. Almost all the authors have made at our request a gigantic effort, for which we are happy to heartily thank them, to render the contents of their Course accessible to non specialists: in the present instance, this School was directed to experimental physicists with the hope to develop the basis for joint investigations on long-range order in solids. We also are particularly grateful to the following colleagues who generously provided help in shaping this book: E. Cockayne, R. Collela, M. Dekking, F. Delyon, F. Denoyer, F. Gahler, A. Janner, T. Janssen, P. Kramer, M. Mendes France, M. Queffelec, S. Van Smaalen. This very intense moment of scientific communication between mathematicians, physicists and material scientists, and this book would never have existed without the constant encouragement of Michele Leduc (Directeur du Centre de Physique des Houches), her very competent and helping staff in Les Houches Mesdames G. Chioso et B. Rousset, and Madame Grosseaux's efficiency and patience (Les Editions de Physique/Springer-Verlag); we would like them to accept the expression of our sincere gratitude. But particular acknowledgements, particular thanks, are due to Madame Fran~oise Kakou. She took care of the entire administrative organization of the School, of the preparation of this book and its annexes with her usual perfect skill, competence, efficiency and kindness, without which we would not have succeeded. Readers, be merciful: if you find errors of any kind, please write to us in view of future printings ... Fran~oise Axel Denis Gratias CONTENTS Quasicrystals COURSE 1 Quasicrystals, diophantine approximation and algebraic numbers by Yves Meyer 1. Introduction.................................................................................... 3 2. Almost-periodic functions. Poisson summation formula and algebraic numbers.. .... 5 3. Model sets and quasicrystals. ................................................................ 9 4. Quasicrystals and diophantine approximation. .. .. . . . . . .. .. . . . . .. . .. . .. . . . . .. . .. . . . .. . .. .. . 10 5. Poisson summation formula and quasicrystals ............. ..................... .......... 14 6. Conclusion ...... ...... ......... ...... .......................................................... 15 COURSE 2 The pentacrystals by J. Patera 1. Introduction... . . . .. . .. . .. . . .. . . .. . .. . . .. .. . .. . .. .. . . .. .. . . .. .. . . . . . .. . .. . .. . . .. . .. .. . . .. . .. .. .. 17 2. Preliminaries.......... ......................................................................... 18 3. The pentacrystal map. ......................................................................... 20 4. DefInition of quasicrystals. . . . .. . .. . . .. .. . .. .. .. . . . .. . .. . .. .. .. .. . .. . . .. . .. . . .. . .. . . . .. .. . .. . . 22 5. Phasons......................................................................................... 23 6. Quasiaddition .................................................................................. 24 7. Examples....................................................................................... 25 COURSE 3 Elements of a multimetrical crystallography by A. Janner Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . ... . . . . .. . . . . . ... . . . . . .. . . . .. . . . . . . . . . . . . .. . . . . . .. .. . . . . . 33 1. Introduction.................................................................................... 33 2. Close-packed structures.. . . . . . .. . . . .. ... . .. . . .. .. .. .. . .. .. . . . . . .. .. . .. . . .. . .. .. .. . .. . .. . . . . .. 35 2.1 The 2-dimensional case.................................................................. 35 2.2 The 3-dimensional case.................................................................. 35 3. Multimetrical symmetry of the 20 hexagonal lattice...... .. ....... ........ ..... ...... ..... 37 4. Binary integral quadratic forms and quadratic fIelds. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 39 5. IndefInite ternary integral quadratic forms.................................................. 41 6. Quadratic forms oflattices of3D close-packed structures.. .. .. .. .. ... .. .. .. . .. .. . . .. .. .. 44 6.1 Reduced metric tensors.................................................................. 44 6.2 IndefInite binary quadratic forms....................................................... 45 6.3 IndefInite ternary quadratic forms ...................................................... 46 7. Multimetrical point group of the hexagonal close-packed lattice. . . ... . . . . .. . . . . . . . . . . . . . 47 8. Multimetrical space groups of crystal structures...... ......... .... ............... ..... .... 49 VIII 8.1 Hexagonal close-packed structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 8.2 The Wurtzite structure. .................................................................. .... 51 9. Concluding remarks........................................................................... 52 COURSE 4 Non-commutative models for quasicrystals by P. Kramer and J. Garcia-Escudero 1. Why non-commutative models for quasicrystals ? .................................... .... 55 2. Free groups and their automorphisms ................. . . . . . . . . . . . . . . . . . . .. . . .. .. . .. . . . . . . . . 56 3. Non-commutative crystallography..................... ... .................................. 57 4. Structure and geometry of the group Aut(F2) .. • • .. • • • • • .. • • .. • .. • .. • .. • • .. • .. • .. .. • .. • • • • • 58 5. Free groups and automorphisms for n > 2 ................................................ 66 6. Non-commutative models and symmetries for 2D quasiperiodic patterns.............. 66 7. Automata for the triangle and Penrose patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 8. Survey of other results.. .. . .. . . . . .. . .. . .. . .. . .. . . .. . . . . .. . . .. . . .. . .. . .. . .. . .. . . .. .. . .. . . . . . . . . 72 COURSE 5 From quasiperiodic to more complex systems by T. Janssen 1. Structures........ .................................................................. ... .......... 75 1.1 Introduction ............................................................................... 75 1.2 Classes of quasiperiodic structures. .. . .. . . . . . . .. . . .. . .. . .. . .. . . .. . .. . . . . . .. . . . . . . .. .. . . 78 1.3 Embedding of quasiperiodic systems.................................................. 81 1.4 Superspace groups.................................................... ................... 84 1.5 Action of symmetry groups in 3-dimensional space.............. . . . . . . . . . . . . . . . .. . . 86 1.6 Scale symmetries......................................................................... 89 1.7 Hierarchy of structures .................................................................. 91 1.8 Physical origin of quasiperiodicity . . .. . . .. . . .. . .. . .. . . .. . . . . .. . . . . .. . . .. . . . . . . . . . . . . .. . 93 2. Diffraction............. . . .. . . . .. . . . . . .. . .. . . . . .. . . .. . . .. . .. . .. . . . . . . . . . . . . .. . .. . . . . .. . .. . . . . . .. . 94 2.1 Structure factor. . .. . . . . .. .. . . . . . .. . .. . .. . .. . .. . . .. . .. . . . . . . . . . . . .. . . .. . . . . .. . .. . .. . . . . . . . . 94 2.2 Structure factor of quasiperiodic structures .............................. . . . . . . . . . .. . . 97 2.3 Influence of symmetry ................................................... ................ 99 2.4 Thermal vibrations ....................................................................... 100 2.5 Disorder................................................................................... 101 3. Phonons........................................................................................ 104 3.1 Phonons in IC phases.................................................................... 104 3.2 Spectra..................................................................................... 110 3.3 Phonons in quasicrystals ................................................................ 111 3.4 Neutron scattering from quasiperiodic structures..................................... 116 4. Substitutional chains.......................................................................... 122 4.1 Introduction .................................................................. ............. 122 4.2 Atomic surfaces........................................................................... 124 4.3 Fractal atomic surfaces................................................................... 127 5. Electrons........................................................................................ 132 5.1 Models..................................................................................... 132 5.2 Spectra..................................................................................... 135 5.3 Wave functions........................................................................... 136 IX COURSE 6 Matching rules and quasiperiodicity: the octagonal tHings by A. Katz 1. Introduction........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 2. Quasiperiodic tHings..................................... ..................................... 142 2.1 Quasiperiodicity ......................... ................................................. 142 2.2 The atonric surfaces ............... ......... ... ......... ... ... ... ... ...... ......... ... .... 143 2.3 The cut algorithm... ... ...... ......... ... ................ ............ ... ........ ... ....... 144 2.4 Canonical or "Penrose like" tilings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 2.4.1 Definition............................................................................ 144 2.4.2 The oblique tiling................................................................... 145 2.4.3 Octagonal tHings. ........................... ... ............ ... ..... .......... ....... 146 3. The composition-decomposition method................................................... 148 3.1 Self-sinrilarity............................................................................. 148 3.2 Inflation and quasiperiodicity............................ ............................... 150 4. The method of forbidden planes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 4.1 Position of the problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 4.2 Non-transversality conditions. ...... ... ................................................. 153 4.3 The forbidden planes..... ...................................................... ... ....... 154 5. Decoration of the tiles....... ........ .................. ............ ...... ... ................... 156 5.1 A simple case. .......... ........ ..................... ......... ... ... ... ............... .... 156 5.2 The Ammann decoration of vertices......... ........................... ... ... ....... ... 159 6. The main theorem............................ ....................................... ... ....... 162 6.1 Position and intersections of the forbidden planes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 6.2 Systems of data.................................................. ... ........ .............. 163 6.3 Propagation of order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 6.4 Proof of the theorem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 6.4.1 The pushing procedure............... .................................... .......... 166 6.4.2 The cone of planes................................................................. 168 6.5 Quasiperiodic tilings and "special tilings" .................... ........................ . 170 7. Generalised Ammann tilings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 7.1 Definitions................................................................................. 174 7.2 Symmetry considerations.................. .......................................... .... 174 7.3 Setting the method........................................................................ 175 7.3.1 Systems of data in £1........................................................ ....... 177 7.4 Reduction to "bad prisms" .......................................................... .... 177 7.5 Proof of the theorem.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 7.6 Order in generalised Ammann tilings of the [ust kind ............ . . . . . . . . . . . . . . . . .. . 181 7.7 Generalised Ammann tilings of the second kind: an example of weak: rules. . . . . . 183 8. Conclusion..................................................................................... 188 COURSE 7 A mechanism for diffusion in quasicrystals by P. A. Kalugin............................................................................... 191 COURSE 8 Experimental aspects of the structure analysis of aperiodic materials by W. Steurer 1. Introduction................................................................................... . 203 2. What are aperiodic materials ? ............................................................... 204 3. Experimental probes for distinguishing between crystals and aperiodic structures.... 206