Special Issue "Modularity and Twinning in Mineral Crystal Structures"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (28 May 2021) | Viewed by 7496

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Special Issue Editor

Prof. Dr. Giovanni Ferraris
E-Mail Website
Guest Editor
1. Dipartimento di Scienze della Terra, Umiversità di Torino, Turin, Italy
2. Accademia Nazionale dei Lincei, Italy, Rome, Italy
Interests: crystallography; mineral crystal structures; mineral crystal chemistry; modular structures; twinning; history of crystallography; local history

Special Issue Information

Dear Colleagues,

In 2004, the book Crystallography of Modular Materials (IUCr/Oxford University Press) by G. Ferraris, E. Makovicky and S. Merlino (2nd edition 2008) systematically reviewed theory and examples of mineral crystal structures that can be described as built up by periodic repetition at atomic scale of either one (planar) module (polytypes) or more - m1, m2, … mn - modules with different composition (polysomes). Whereas a series of polytypes, being based on a same module, shows essentially a constant chemical composition, the members of a polysomatic series have different chemical compositions that depends on the ratio m1/m2… /mn. In a polysomatic series, the physical properties are a function of the chemistry of the modules and of their piling; thus, tailoring of the properties is possible. A special class of polytypes is rationalized by the so-called OD (Order/Disorder) theory. Twinning, i.e., the oriented association of two or more individuals of the same crystalline compound, is considered a modular structure at macroscopic scale. The members of a series of polytypes or of polysomes have usually in common a supercell that, according to the reticular theory of twinning, favours the formation of twins. The nature, nomenclature, and bibliography of twinning are well summarized in the following web site http://www.crystallography.fr/mathcryst/twins.htm

Authors are invited to submit both experimental and theoretical articles dealing with the purposes of the Special Issue.

Prof. Dr. Giovanni Ferraris
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Modular structures
  • Polytypes (single structures)
  • Polytypes (series)
  • Polysomes (single structures)
  • Polysomes (series)
  • Modularity and tailoring of physical properties
  • Twinning (morphology)
  • Twinning (diffraction patterns)
  • Twinning (structure refinement)
  • Twinning (detection of)
  • Twinning and genetic conditions
  • Hybrid twins
  • Plesiotwins

Published Papers (8 papers)

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Editorial

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Editorial
Editorial for the Special Issue “Modularity and Twinning in Mineral Crystal Structures”
Minerals 2021, 11(7), 758; https://doi.org/10.3390/min11070758 - 14 Jul 2021
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Abstract
Ferraris et al [...] Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)

Research

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Article
Diffraction Features from (101¯4) Calcite Twins Mimicking Crystallographic Ordering
Minerals 2021, 11(7), 720; https://doi.org/10.3390/min11070720 - 04 Jul 2021
Cited by 1 | Viewed by 995
Abstract
During phase transitions the ordering of cations and/or anions along specific crystallographic directions can take place. As a result, extra reflections may occur in diffraction patterns, which can indicate cell doubling and the reduction of the crystallographic symmetry. However, similar features may also [...] Read more.
During phase transitions the ordering of cations and/or anions along specific crystallographic directions can take place. As a result, extra reflections may occur in diffraction patterns, which can indicate cell doubling and the reduction of the crystallographic symmetry. However, similar features may also arise from twinning. Here the nanostructures of a glendonite, a calcite (CaCO3) pseudomorph after ikaite (CaCO3·6H2O), from Victoria Cave (Russia) were studied using transmission electron microscopy (TEM). This paper demonstrates the occurrence of extra reflections at positions halfway between the Bragg reflections of calcite in 0kl electron diffraction patterns and the doubling of d104 spacings (corresponding to 2∙3.03 Å) in high-resolution TEM images. Interestingly, these diffraction features match with the so-called carbonate c-type reflections, which are associated with Mg and Ca ordering, a phenomenon that cannot occur in pure calcite. TEM and crystallographic analysis suggests that, in fact, (101¯4) calcite twins and the orientation change of CO3 groups across the twin interface are responsible for the extra reflections. Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)
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Article
Polytypism of Compounds with the General Formula Cs{Al2[TP6O20]} (T = B, Al): OD (Order-Disorder) Description, Topological Features, and DFT-Calculations
Minerals 2021, 11(7), 708; https://doi.org/10.3390/min11070708 - 30 Jun 2021
Cited by 3 | Viewed by 603
Abstract
The crystal structures of compounds with the general formula Cs{[6]Al2[[4]TP6O20]} (where T = Al, B) display order-disorder (OD) character and can be described using the same OD groupoid family. Their structures are [...] Read more.
The crystal structures of compounds with the general formula Cs{[6]Al2[[4]TP6O20]} (where T = Al, B) display order-disorder (OD) character and can be described using the same OD groupoid family. Their structures are built up by two kinds of nonpolar layers, with the layer symmetries Pc(n)2 (L2n+1-type) and Pc(a)m (L2n-type) (category IV). Layers of both types (L2n and L2n+1) alternate along the b direction and have common translation vectors a and c (a ~ 10.0 Å, c ~ 12.0 Å). All ordered polytypes as well as disordered structures can be obtained using the following partial symmetry operators that may be active in the L2n type layer: the 21 screw axis parallel to c [– – 21] or inversion centers and the 21 screw axis parallel to a [21 – –]. Different sequences of operators active in the L2n type layer ([– – 21] screw axes or inversion centers and [21 – –] screw axes) define the formation of multilayered structures with the increased b parameter, which are considered as non-MDO polytypes. The microporous heteropolyhedral MT-frameworks are suitable for the migration of small cations such as Li+, Na+ Ag+. Compounds with the general formula Rb{[6]M3+[[4]T3+P6O20]} (M = Al, Ga; T = Al, Ga) are based on heteropolyhedral MT-frameworks with the same stoichiometry as in Cs{[6]Al2[[4]TP6O20]} (where T = Al, B). It was found that all the frameworks have common natural tilings, which indicate the close relationships of the two families of compounds. The conclusions are supported by the DFT calculation data. Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)
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Article
Rb1.66Cs1.34Tb[Si5.43Ge0.57O15]·H2O, a New Member of the OD-Family of Natural and Synthetic Layered Silicates: Topology-Symmetry Analysis and Structure Prediction
Minerals 2021, 11(4), 395; https://doi.org/10.3390/min11040395 - 09 Apr 2021
Cited by 2 | Viewed by 750
Abstract
Crystals of new silicate-germanate Rb1.66Cs1.34Tb[Si5.43Ge0.57O15]·H2O have been synthesized hydrothermally in a multi-component system TbCl3:GeO2:SiO2 = 1:1:5 at T = 280 °C and P = 100 atm. [...] Read more.
Crystals of new silicate-germanate Rb1.66Cs1.34Tb[Si5.43Ge0.57O15]·H2O have been synthesized hydrothermally in a multi-component system TbCl3:GeO2:SiO2 = 1:1:5 at T = 280 °C and P = 100 atm. K2CO3, Rb2CO3 and Cs2CO3 were added to the solution as mineralizers. The crystal structure was solved using single crystal X-ray data: a = 15.9429(3), b = 14.8407(3), c = 7.2781(1) Å, sp. gr. Pbam. New Rb,Cs,Tb-silicate-germanate consists of a [Si5.43Ge0.57O15]∞∞ corrugated tetrahedral layer combined by isolated TbO6 octahedra into the mixed microporous framework as in synthetic K3Nd[Si6O15]·2H2O, K3Nd[Si6O15] and K3Eu[Si6O15]·2H2O with the cavities occupied by Cs, Rb atoms and water molecules. Luminescence spectrum on new crystals was obtained and analysed. A comparison with the other representatives of related layered natural and synthetic silicates was carried out based on the topology-symmetry analysis by the OD (order-disorder) approach. The wollastonite chain was selected as the initial structural unit. Three symmetrical ways of forming ribbon from such a chain and three ways of further connecting ribbons to each other into the layer were revealed and described with symmetry groupoids. Hypothetical structural variants of the layers and ribbons in this family were predicted. Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)
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Article
Twinning, Superstructure and Chemical Ordering in Spryite, Ag8(As3+0.50As5+0.50)S6, at Ultra-Low Temperature: An X-Ray Single-Crystal Study
Minerals 2021, 11(3), 286; https://doi.org/10.3390/min11030286 - 10 Mar 2021
Cited by 1 | Viewed by 815
Abstract
Spryite (Ag7.98Cu0.05)Σ=8.03(As5+0.31Ge0.36As3+0.31Fe3+0.02)Σ=1.00S5.97, and ideally Ag8(As3+0.5As5+0.5)S6, is a new mineral recently described from [...] Read more.
Spryite (Ag7.98Cu0.05)Σ=8.03(As5+0.31Ge0.36As3+0.31Fe3+0.02)Σ=1.00S5.97, and ideally Ag8(As3+0.5As5+0.5)S6, is a new mineral recently described from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. Its room temperature structure exhibits an orthorhombic symmetry, space group Pna21, with lattice parameters a = 14.984(4), b = 7.474(1), c = 10.571(2) Å, V = 1083.9(4) Å3, Z = 4, and shows the coexistence of As3+ and As5+ distributed in a disordered fashion in a unique mixed position. To analyze the crystal-chemical behaviour of the arsenic distribution at ultra-low temperatures, a structural study was carried out at 30 K by means of in situ single-crystal X-ray diffraction data (helium-cryostat) on the same sample previously characterized from a chemical and structural point of view. At 30 K, spryite still crystallizes with orthorhombic symmetry, space group Pna21, but gives rise to a a × 3b × c superstructure, with a = 14.866(2), b = 22.240(4), c = 10.394(1) Å, V = 3436.5(8) Å3 and Z = 4 (Ag24As3+As5+Ge4+S18 stoichiometry). The twin laws making the twin lattice simulating a perfect hexagonal symmetry have been taken into account and the crystal structure has been solved and refined. The refinement of the structure leads to a residual factor R = 0.0329 for 4070 independent observed reflections [with Fo > 4σ(Fo)] and 408 variables. The threefold superstructure arises from the ordering of As3+ and (As5+, Ge4+) in different crystal-chemical environments. Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)
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Article
A Mero-Plesiotype Series of Vanadates, Arsenates, and Phosphates with Blocks Based on Densely Packed Octahedral Layers as Repeating Modules
Minerals 2021, 11(3), 273; https://doi.org/10.3390/min11030273 - 07 Mar 2021
Cited by 1 | Viewed by 782
Abstract
The family of layered vanadates, arsenates, and phosphates is discussed in terms of a modular concept. The group includes minerals vésignéite and bayldonite, and a number of synthetic analogous and modifications which are not isotypic, but their crystal structures comprise similar blocks (modules) [...] Read more.
The family of layered vanadates, arsenates, and phosphates is discussed in terms of a modular concept. The group includes minerals vésignéite and bayldonite, and a number of synthetic analogous and modifications which are not isotypic, but their crystal structures comprise similar blocks (modules) consisting of a central octahedral layer filled by atoms of d elements (Mn, Ni, Cu, or Co) and adjacent [VO4], [AsO4], or [PO4] tetrahedra. The octahedral layers are based on the close-packing of oxygen atoms. Within these layers having the same anionic substructure, the number and distribution of octahedral voids are different. In the crystal structures of compounds participating in the polysomatic series, these blocks alternate with various other structural fragments. These circumstances define the row of structurally-related vanadates, arsenates, and phosphates as a mero-plesiotype series. Most of the series members exhibit magnetic properties, representing two-dimensional antiferromagnets or frustrated magnets. Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)
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Article
Twinning of Tetrahedrite—OD Approach
Minerals 2021, 11(2), 170; https://doi.org/10.3390/min11020170 - 07 Feb 2021
Cited by 1 | Viewed by 864
Abstract
The common twinning of tetrahedrite and tennantite can be described as an order–disorder (OD) phenomenon. The unit OD layer is a one-tetrahedron-thick (111) layer composed of six-member rings of tetrahedra, with gaps between them filled with Sb(As) coordination pyramids and triangular-coordinated (Cu, Ag). [...] Read more.
The common twinning of tetrahedrite and tennantite can be described as an order–disorder (OD) phenomenon. The unit OD layer is a one-tetrahedron-thick (111) layer composed of six-member rings of tetrahedra, with gaps between them filled with Sb(As) coordination pyramids and triangular-coordinated (Cu, Ag). The stacking sequence of six-member rings is ABCABC, which can also be expressed as a sequence of three consecutive tetrahedron configurations, named α, β, and γ. When the orientation of component tetrahedra is uniform, the α, β, γ, α sequence builds the familiar cage structure of tetrahedrite. However, when the tetrahedra of the β layer are rotated by 180° against those in the underlying α configurations and/or when a rotated α configuration follows after the β configuration (instead of γ), twinning is generated. If repeated, this could generate the ABAB sequence which would modify the structure considerably. If the rest of the structure grows as a regular cubic tetrahedrite structure, the single occurrence of the described defect sequences creates a twin. Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)
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Review

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Review
Ferroelastic Twinning in Minerals: A Source of Trace Elements, Conductivity, and Unexpected Piezoelectricity
Minerals 2021, 11(5), 478; https://doi.org/10.3390/min11050478 - 30 Apr 2021
Cited by 1 | Viewed by 839
Abstract
Ferroelastic twinning in minerals is a very common phenomenon. The twin laws follow simple symmetry rules and they are observed in minerals, like feldspar, palmierite, leucite, perovskite, and so forth. The major discovery over the last two decades was that the thin areas [...] Read more.
Ferroelastic twinning in minerals is a very common phenomenon. The twin laws follow simple symmetry rules and they are observed in minerals, like feldspar, palmierite, leucite, perovskite, and so forth. The major discovery over the last two decades was that the thin areas between the twins yield characteristic physical and chemical properties, but not the twins themselves. Research greatly focusses on these twin walls (or ‘twin boundaries’); therefore, because they possess different crystal structures and generate a large variety of ‘emerging’ properties. Research on wall properties has largely overshadowed research on twin domains. Some wall properties are discussed in this short review, such as their ability for chemical storage, and their structural deformations that generate polarity and piezoelectricity inside the walls, while none of these effects exist in the adjacent domains. Walls contain topological defects, like kinks, and they are strong enough to deform surface regions. These effects have triggered major research initiatives that go well beyond the realm of mineralogy and crystallography. Future work is expected to discover other twin configurations, such as co-elastic twins in quartz and growth twins in other minerals. Full article
(This article belongs to the Special Issue Modularity and Twinning in Mineral Crystal Structures)
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