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Structural Disorder in Quasicrystals

Strzałka R., Bugański I., Śmietańska J., Wolny J.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

291--294

EN

One of the challenges of modern crystallography of complex systems (complex metallic alloys, proteins, aperiodic crystals and quasicrystals) is to properly describe the disorder in these systems and discuss correctly the refinement results in terms of the structural disorder. In this paper we briefly discuss a new approach to phasons and phonons in quasicrystals and focus on the new theory of phonons in these materials. A newly derived correction factor for phonons in the form of the Bessel function is the approximated way of describing optic modes in the phonon spectra of quasicrystals. It is applied to a real decagonal quasicrystal in the Al-Cu-Rh system with 56/38 atoms per thick/thin structural unit, based on 2092 unique reflections selected from the collected diffraction data, significantly improving the refinement results. The final R-factor value is 7.24%, which is over 0.5% better result comparing to originally reported. We believe our work will open a broader discussion on the disorder in quasicrystals (and other aperiodic systems) and motivate to develop new approaches to treat the diffraction data influenced by different types of disorder in the new way.

2

Statistical Description of Diffraction Pattern of Aperiodic Crystals

Wolny J., Bugański I., Pytlik L., Strzałka R.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

721--725

EN

Modern crystallography faces a demanding challenge of describing atomic structure and diffraction pattern of quasicrystals, which, after 30 years of Shechtman’s discovery, is still an open field of research. The classical approach based on the Braggs and Laue equations in three-dimensional space is useless, because the direct and the reciprocal lattices cannot be introduced for aperiodic systems. A standard solution to this problem, applied by number of scientists, is to retrieve periodicity in high dimensions. This is a purely mathematical approach with some difficulties from a point of view of physics. It is mathematically elegant, but not applicable to all aperiodic systems (e.g. Thue-Morse or Rudin-Shapiro sequences). It meets also a serious trouble in a proper description of structural defects, like phasons. In our opinion the most successful alternative to the multidimensional description is a statistical method of diffractional and structural analysis of aperiodic systems, also known as the average unit cell approach (AUC). In this work an application of the AUC method to selected aperiodic systems, including modulated structures, quasicrystals and covering clusters, is discussed in the form of a mini-review. A reader can find more details in the cited references.

3

Lokalny model aktywizacji społecznej i zawodowej osób z niepełnosprawnością intelektualną

Wolny J.

Zeszyty Naukowe. Organizacja i Zarządzanie / Politechnika Śląska

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2018

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z. 132

675--687

PL

Prezentowany artykuł stanowi propozycję kompleksowych rozwiązań w zakresie aktywizacji społecznej i zawodowej osób z umiarkowaną niepełnosprawnością intelektualną lub osób z chorobami psychicznymi w lokalnym środowisku z uwzględnieniem aktywnej współpracy struktur samorządowych, podmiotów edukacji, pomocy społecznej i służb odpowiedzialnych za lokalną politykę zatrudnienia z sektorem przedstawicieli biznesu jako potencjalnych pracodawców oraz funkcjonującymi w regionie ośrodkami akademickimi. Opisywany model osadzony jest w paradygmacie humanistycznym i jego istotnych dla pedagogiki specjalnej pochodnych, tj. w paradygmacie społecznym, emancypacyjnym i normalizacyjnym (Krause, 2010, s. 118), uwzględnia więc te elementy współczesnej myśli społecznej, które próbują postrzegać osoby z niepełnosprawnościami w szerszym kontekście „inności” i „innych”, w tym przypadku jednostek pozostających dotychczas poza normą i ich miejsca w społeczeństwie, ich prawa dokonywania wyborów, także w zakresie wyboru różnych form egzystencji (por. tamże). Opisywany w artykule model pozwala, w przypadku jego wdrożenia, na niezależne, samodzielne życie dużej grupy osób z niepełnosprawnościami, tworząc jednocześnie pragmatyczne i bardziej ekonomicznie uzasadnione rozwiązania w lokalnym środowisku.

EN

Presented article is above all a very specific proposal of comprehensive solutions in the field of social and professional activation of people with intellectual disability, may also be for people with mental illness in the local environment, including active cooperation of the self-government (schools, social welfare services and employment services) with the environment of local entrepreneurs, business and the university. Described model is embedded in the humanistic paradigm and its essential in special pedagogy, derived from the social paradigm, emancipation and normalization paradigm (Krause, 2010, p. 118), thus these elements in contemporary social thought, which try to perceive people with disabilities in the broader context of "otherness" and "other", in this case, individuals who have remained outside the norm and their place in society, their right to different forms of existence, choices and alternatives (Krause, 2010, p. 118). In general, it can be stated that the model described in this article allows for independent living of a large group of people with disabilities, while creating pragmatic and more economically justified solutions in the local environment.

4

Structure of decagonal quasicrystals described by clusters

Kozakowski B, Duda M, Wolny J

Materials Science Poland

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2008

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Vol. 26, No. 4

903--912

EN

The cluster model offers a new approach to the structure of quasicrystals. The model assumes that the whole structure can be covered by only one structure unit – the cluster. However, because quasicrystals are not periodic, clusters must overlap each other. The first known cluster is G33 proposed by Gummelt. Another type of cluster is the kite cluster – it is the smallest possible cluster that can cover the whole Penrose tiling. There are three different kite clusters: 17-atom K17, 7-atom K7 and 4-atom K4 discussed in the paper.