Nanoscience of Quasicrystals and Related Complex Metallic Alloys

Lead Research Organisation: University of Liverpool
Department Name: Physics


When a pattern has a basic repeating element, like a square tile in a tiled bathroom, we say the pattern is periodic. The concept of periodicity is a simple one, but its consequences are far reaching. Periodic systems possess long-range order; in other words if we know the position of the first tile in the pattern, then the positions of all the other tiles in the pattern can be found just by shifting this tile along by regular increments. This only works for a very limited number of simple shapes, among them squares, triangle and hexagons. Try covering a surface with pentagons. There will always be gaps in a tiling made in this way. Until twenty years ago, it was thought that materials were either ordered in a periodic way as described above (in which case they were called crystals), or completely disordered (in which case they were said to be amorphous). Nearly all the physical properties of materials were found to depend on whether the material was crystalline or amorphous.In 1984 a class of materials were discovered which are in between crystals and amorphous materials in terms of their structure. They are known as quasicrystals. They have long-range order, in the sense that their structure can be built up from some simple rules. Their structure is in fact based on a minimum of two tiles which have very specific shapes. When the tiles are put together with some rules as to which edges of the tiles should match, then a quasiperiodic pattern is built up. This is known as a Penrose tiling. Quasicrystals can be thought of as Penrose tilings with groups of atoms attached to the corners of the tiles to give them atomic structure.The study of the properties of quasicrystals in the past 20 years has allowed scientists to understand the effects of this new kind of order in a real physical system. In particular we have learned much about the behaviour of electrons, which are the conductors of electricity in materials, and about magnetism in a new context. These studies have occurred in parallel with huge developments in science in the past 10 years which have focussed on extremely small scale atomic arrangements called nanostructures, and the potential applications of these nanostructures, a field called nanotechnology. This proposal is to join these two areas together, that is quasicrystals and nanoscience, through a number of different approaches which include:(i) the study of nanoscale structures which are grown on quasicrystal surfaces by sprinkling tiny amounts of atoms on the surfaces and letting them organize themselves into overlayers or thin films;(ii) The use of systems created in step (i) above as templates for ordered molecular adsorption;(iii) the study of what happens the surfaces of quasicrystals when they are placed in a conducting liquid environment where the conditions and hence the state of the surface may be strictly controlled - this is known as electrochemistry;(iv) the study of periodic crystalline materials which are closely related to quasicrystals themselves - we call these complex metallic alloys.The main tool which will be used to perform these studies is an instrument known as a scanning tunnelling microscope. This is a microscope which allows us make images of atoms on surfaces in a relatively quick and controlled way.We intend the outcome of the proposal to be a substantially increased understanding of what happens in nanoscale systems which have a quasicrystalline nature. We should understand much more about the electrical, thermal, magnetic and structural properties of these systems, and have some ideas about which applications of these materials might be feasible.


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Description IN2P3 CNRS 
Organisation National Center for Scientific Research (Centre National de la Recherche Scientifique CNRS)
Department IN2P3 CNRS
Country France 
Sector Academic/University 
Start Year 2006