Special issue “Deciphering the complexity of mineral structures”

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Marco E. Ciriotti
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Special issue “Deciphering the complexity of mineral structures”

Messaggio da Marco E. Ciriotti » lun 12 feb, 2018 11:03

Prossima pubblicazione.

Referenza:
▪ Bindi, L. & Plášil, J. (2018): Special issue “Deciphering the complexity of mineral structures”. Zeitschrift für Kristallographie - Crystalline Materials, 233, (in press).

Abstract:
https://www.degruyter.com/view/j/zkri.a ... 8-9001.png
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 24492
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: Special issue “Deciphering the complexity of mineral structures”

Messaggio da Marco E. Ciriotti » ven 13 apr, 2018 12:23

Referenza:
▪ Bindi, L. & Plášil, J. (2018): Special issue “Deciphering the complexity of mineral structures”. Zeitschrift für Kristallographie - Crystalline Materials, 233, 153-154.

Mineral structures have always represented a treasure trove for new discoveries in crystallography. For example, in the field of aperiodic crystallography, the mineral calaverite (Au1−xAgxTe2, with 0≤x≤0.33) was an ideal case to begin to shed light on incommensurability in crystals [1]. Later, mineralogy played an important role with numerous examples of mineral structures exhibiting non-commensurate (misfit) layer structures [2], currently known under the name of composite structures, and in providing the first example of a (billion years old) natural quasicrystal [3], which settled any doubt that could remain on the long-term stability of quasicrystals.

The special issue of the Zeitschrift für Kristallographie on the complexity of mineral structures contains 10 contributions. While the first three articles are more general (intrinsic aspects of structural complexity), or methodological (electron diffraction tomography) or deal with more theoretical aspects of crystallography (structure description based on the sphere packing), the other seven articles are related to structure solutions of complicated, still unknown mineral structures. These papers include solutions and refinements of structures of silicates [swamboite-(Nd) and seidozerite-supergroup minerals], uranyl sulfates/selenates, sulfosalts (roshchinite, zinkenite, and semseyite), and tellurides (stützite). There are examples of modulated mineral structures deciphered with multidimensional structure refinements in superspace [swamboite-(Nd) and roshchinite], complex twinned superstructures (zinkenite), disordered structures solved using the Gram-Charlier development of atomic displacement factors (stützite), or structures with a very large number of atoms in the unit cell (seidozerite-supergroup minerals).

The research dealing with the complexity of mineral structures is continually moving forward. In recent years, the use of CCD and imaging plate systems considerably improved the sensitivity of data collection for complex mineral structures, in particular incommensurately modulated structures. Several computer programs are nowadays able to solve and refine incommensurately modulated structures using the superspace approach and easily deal with structures characterized by strong pseudo-symmetry and twinning. Beside X-ray diffraction, precession electron diffraction methods allow us to determine the structure from very small particles, down to a few nanometers.

Given this extraordinary range of techniques and instrumentations, we think that, beside the ongoing work to determine still-unknown mineral structures, a broader vision is called for in considering the future of mineralogical crystallography. Minerals whose diffraction patterns consist of sharp reflections are well studied by now, but recently there have been interesting investigations of matter with long-range correlations but no sharp reflections at all. An example is a new class of solids called “hyperuniform disordered” [4, 5], homogeneous materials with the short-to-intermediate characteristics of a glass (isotropic, random) and the long-range characteristics of a crystal (density fluctuations that grow as the surface area rather than the volume). Hyperuniform disordered solids are potentially important because they have large band gaps despite the lack of translational order, resulting in novel types of semiconductors. We think that the stability of hyperuniform disordered solids, their ease of manufacture and their variety of compositions suggest that they may be an as yet undiscovered component of the mineral kingdom awaiting the careful inspection of a diligent mineral collector who does not disregard ‘crystallographic oddities’ a priori.

The discovery of quasicrystals in nature [3] showed us that it could probably be the tip of a huge iceberg of novel materials to be discovered in the mineral kingdom. Our ability to discover them in Nature is limited only by the human imagination. Our hope is to see in a near future many new classes of novel materials that have yet to be envisioned. Mineralogy can continue to surprise us and have a strong impact on other disciplines, including chemistry, condensed matter physics, materials engineering and cosmochemistry.

Last but not least, we would like to express our gratitude to Vaclav Petříček, who raised the idea of the special issue on the complexity of mineral structures, and to Rainer Pöttgen, who made the idea become reality understanding the prominent role of mineralogical crystallography in the advancements of structural science. Finally, special thanks go to the authors, who rapidly and efficiently prepared their research articles.


References


[1]

V. Goldschmidt, C. Palache, M. Peacock, M. Über Calaverit, N. Jahr. Mineral. Monat. 1931, 63, 1. 
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[2]

E. Makovicky, B. G. Hyde, Non-commensurate (misfit) layer structures. Inorg. Chem. 1981, 46, 101. 
 Crossref Google Scholar


[3]

L. Bindi, P. J. Steinhardt, N. Yao, P. J. Lu, Natural quasicrystals. Science 2009, 324, 1306. 
 Crossref Web of Science Google Scholar


[4]

S. Torquato, F. H. Stillinger, Local density fluctuations, hyperuniformity, and order metrics. Phys. Rev. 2003, 68, 1. 
 Google Scholar


[5]

M. Florescu, S. Torquato, P. J. Steinhardt, Designer materials with large, complete photonic band gaps. Proc. Nat. Acad. Sci. USA 2009, 106, 20658. 
 Crossref Google Scholar
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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