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About Conference
6th International Conference on Aperiodic Crystals
Liverpool, 13 – 18 September 2009
Sixth International Conference on Aperiodic Crystals (Aperiodic ‘09) was organized under the auspices of the Commission on Aperiodic Crystals of the International Union of Crystallography (IUCr). This triennial series conference was earlier held as Aperiodic’94 at Les Diablerets, Aperiodic’97 at Alpe d’Huez, Aperiodic’2000 at Nijmegen, Aperiodic’03 at Belo Horizonte and Aperiodic’ 06 at Zao. The account of the conference Aperiodic- 2000 (Nijmegen, The Netherlands) was reported earlier (Current Sciences 79 (2000) 1637). In 1988, this conference series was known as ‘Modulated Structure, Polytypes and Quasicrystals’, (MOSPOQ) and it was organized in IT-BHU, by P. Ramachandra Rao (chair), S. Lele (co-chair) and D. Pandey (convener).
R. McGrath and U. Grimm (co-chairs) organized the Aperiodic’09 conference from 13-18 September 2009 in the Liverpool University (http://www.liv.ac.uk) at Liverpool, which was considered as a European Capital of Culture in 2008. About 110 participants attended from all over the country. Prof N.K. Mukhopadhyay, Professor, Department of Metallurgical Engineering, IT-BHU attended this conference along with his doctoral student T.P. Yadav. Prof Mukhopadhyay, being a member of the Aperiodic Commission of IUCr was invited to chair a technical session. He also delivered a talk on the phase transformation of quasicrystalline materials during high energy ball milling. The details of the conference and the abstract of the papers presented in the conference can be found at: http://www.aperiodic09.org/. There were about 100 papers presented in fifteen oral (44 papers) and two poster (45 papers) sessions including one tutorial (3 papers) sessions. The proceedings containing the selected papers after peer review will be published in the Journal of Physics Conference Series (open access). It is worth mentioning that there was an interesting public lecture delivered by Professor Sir Roger Penrose (UK) (shown in photo 1), who discovered the quasiperiodic tiling, now popularly known by his name as Penrorse Tiling. He elegantly demonstrated that how the simple sets of shapes that tile the plane without repetition, gaps and overlaps. Many explicit examples of aperiodic sets were presented in his talk, showing different types of symmetry.
The brochure on conference
The 90-page brochure on conference can be viewed here
aperiodic2009.pdfAperiodic Crystals
In 1994 the name of this conference series changed from ‘MOSPOQ’ to ‘Aperiodic Crystals’ encompassing issues associated to more general class of solids belonging or closely relating to aperiodic crystals. Aperiodic crystals are characterized by the discrete diffraction patterns which cannot be indexed with the conventional three indices but require additional ones. They occur in almost every type of solids including organic and inorganic compounds, minerals, metals and alloys, and even macromolecules. It is convenient to describe their structures in superspace (higher dimensional space), a conceptual environment, in which three-dimensional aperiodic crystals recover their periodicity. The inconvenience of adding extra dimensions is negligible concerning all the advantages resulting from the properties of periodicity (diffraction phenomena, Fourier transform, symmetry etc). The studies of aperiodic structures have greatly contributed to a better understanding of the physics and chemistry of atomic interactions in crystals and it opens up also the new perspectives for correlating the structural with the physical properties of complex materials.
In terms of atomic arrangements, the solids are generally classified into three major groups: (i) Periodic Crystals (ii) Aperiodic Crystals, (iii) Amorphous or glassy phase. The periodic crystals show the periodicity among the atomic arrangements (real space) as well as in the corresponding diffraction patterns (reciprocal space). The rotational symmetries in the diffraction patterns are restricted to 2 fold, 3-fold, 4 fold and 6 fold symmetries, where as the aperiodic crystals exhibit the aperiodicity (i.e., no periodicity but some regularity and order) among the atomic arrangements. The corresponding diffraction patterns are discrete like periodic crystals but not restricted to only those rotational symmetries unlike periodic solids, as indicated above. It is known that the amorphous/glassy phases consist of atoms in a random fashion and it does not show any discrete diffraction patterns. In short, “Aperiodic Crystal" is meant any solid having an essentially discrete diffraction diagram, and in which three-dimensional lattice periodicity can be considered to be absent. As an extension, this term will also include those crystals in which three-dimensional periodicity is too weak to describe significant correlations in the atomic configuration, but which can be properly described by crystallographic methods developed for actual aperiodic crystals.
Aperiodic crystals include modulated structures, polytypes, incommensurate misfit or composite crystals, and quasicrystals. Some of the aperiodic crystals also fall in the category of Complex Metallic Alloys (CMA). Lots of work is being done to understand the basis for synthesis, structure, and stability of these phases. Generally, this class of materials is hard, brittle and of high strength due to the restricted activities of dislocations as the structure is highly complicated. Attempts are also being made to use these materials in the form nanocrystals and nanocomposites. These materials can be applied for suitable coatings on soft substrate and also as suitable reinforcements in the composite materials. In addition to the mechanical properties, these materials also exhibit the unusual physical properties for which the efforts are being made to correlate their structures with the properties.
The unusual electronic and magnetic behaviors also have made these materials interesting for further research. In BHU, namely in the Department of Metallurgy and the School of Materials Science & Technology of IT-BHU, and in the Department of Physics, the research related to the Aperiodic Crystals is being actively pursued.
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Photo: 1: After the technical presentation discussion with Professor Sir Roger Penrose in the conference venue (second from left).
Photo2: Moving around the famous dock on river Mersey (Albert Dock area in Liverpool) which used to be the important centre for business transaction before World War II
Photo 3: Discussing with the Prof. Y. Ishi (Chairman of Int. Conf. quasicrystals (ICQ11) at the conference venue during the tea-break at Liverpool University.
Liverpool City
(Liverpool city)
(Photo: http://heavier-than-air.blogspot.com/2008/03/das-kapital.html)
Founded in 1207, Liverpool has a population of 435,000 (815,000 including suburban areas). There are a diverse population with a wide range of cultures and religions drawn from all over the world, owing to Liverpool’s importance as a port. The city is home to the oldest Black community in Britain, dating from the 1700s and the oldest Chinese community in Europe – the first residents of the city’s Chinatown arrived as seamen in the 1800s.
This importance of the ports on Mersey river at Liverpool has historically led to the city being considered ‘the second city of the Empire’ (Disraeli), ‘the New York of Europe’ (Illustrated London News, 1885) and the ‘pool of life’ (Jung). However, following severe bombing in the Second World War and hurried reconstruction efforts that were then rendered obsolete by modernization of the shipping system, trade went into a sharp decline starting in the 1970s. Today the city is back on an upward trend, being named ‘European Capital of Culture’ in 2008.
Liverpool was the centre in the 1960s of Merseybeat and since then has been home to a music scene. Many musicians, including Michael Jackson consider the city to be the spiritual home of contemporary pop music due to success of ‘The Beatles’, which started by four musicians and became very famous in 1960s.
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Prof. N.K. Mukhopadhyay
Department of Metallurgical Engineering
Institute of Technology
Banaras Hindu University
Varanasi 221 005, INDIA
Email: mukho_nk@rediffmail.com
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Abstract of the paper
Abstract of the Paper co-submitted by Prof. N. K. Mukhopadhyay at the Aperiodic 09 Conference at Liverpool, UK
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Additional Links:
* Official website of Aperiodic ’09 International Conference
* University of Liverpool, UK
http://www.liv.ac.uk/
(University of Liverpool, UK)
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Aperiodic Crystal-An article
http://techon.nikkeibp.co.jp/article/HONSHI/20080304/148429/
Reports Nikkei Electronics Asia -- March 2008
Better Electronics through R&D in Chemistry
Mar 4, 2008 17:09 Nikkei Electronics Asia
A recent discovery in basic chemistry research may pave the way to better electronics in the future. Researchers at Kansas State University have found that certain "aperiodic crystals" become ferroelastic when they change phases so they can be squeezed, opening the door to innovations in future displays, disk drives and other devices that use crystals.
Aperiodic Crystals "Behave Differently"
The researchers at Kansas State University, working with colleagues in France, showed that aperiodic materials, which lack a regularly repeating structure, don't necessarily operate like periodic crystals during phase transitions.
"There are all sorts of rules about what crystals can do during phase transitions," said Mark D Hollingsworth, Associate Professor of chemistry at Kansas State, who worked on the project. "For a long time, scientists have assumed that the norm applied for all sorts of substances."
But in looking at aperiodic crystals, the researchers found they behave differently. They looked at crystals that form a host-guest structure, notably urea molecules that form tunnels around nonadecane molecules to make a honeycomb-like structure. That structure takes the form of a double-helix, similar to the shape of DNA in genetics. In periodic host-guest crystals, the host molecules form the tunnels and the guest molecules inside form a structure that repeats regularly. But in aperiodic host-guest crystals, the host and guest structures don't match: the guest molecules protrude from the ends of the crystals, making the surface rough. This roughness makes it easier to attach new molecules to the ends of the crystals, which are shaped like long needles.
When the crystals transition from one phase to another, there are even more changes under different temperatures. The researchers looked at the guest molecules when they were moving rapidly inside their tunnel-like hosts at higher temperatures, and at extremely cold temperatures as molecules are becoming frozen in place. To examine the crystals, the scientists scattered neutrons from them and measured different reflections. One class of reflections, called satellite reflections, measures the interaction between the guest and host molecules. When the crystal was cooled to about -123oC, the satellite reflections showed a change in the interaction between the host and guest structures, but no noticeable changes to either the host or guest structures themselves.
Hollingsworth said this was a surprise to his team of researchers, because it didn't follow the normal rules about homogenous phase transitions and symmetry breaking. More research is needed to figure out the rules by which these aperiodic crystals function during phase transitions.
Applications in Displays
Hollingsworth said that the crystals are ferroelastic, meaning that the molecules within the crystals reorient when the crystals are squeezed. Closely related ferroelectric materials are important to technology applications, because the domains within such materials can be reoriented with electric fields to permit or prohibit polarized light to pass through, so there are potential applications in electronic displays.
But because their work still is in the research stage, Hollingsworth said they still must see whether the phases they have observed will actually have unusual properties that are useful. He also said he expects the same unusual phase transition behavior to occur in materials other than the urea-nonadecane crystals they used.
by Lori Valigra
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(if you having troubles, try posting your comment on this page or send an email to chronicle @ itbhuglobal.org)Institute of Technology, Banaras Hindu University
Varanasi 221005, UP