Crystallography of Modular Materials

Ferraris, Giovanni; Makovicky, Emil; Merlino, Stefano

doi:10.1093/acprof:oso/9780199545698.001.0001

Cited by 170 publications

(219 citation statements)

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“…The most recent structural interpretation of the bastnäsite-synchysite group, with the general formula: Ca m (REE) n (CO 3 ) n+m (F,OH) n (bastnäsite, m = 0, n = 1; synchysite, m = 1, n = 1; parisite, m = 1, n = 2; röntgenite, m = 2, n = 3 [28]), considers order-disorder (OD) formalism akin to that seen in vaterite [29]. In this case, the polytypism and OD phenomena are attributed only to the Ca-based layer (as in vaterite) whereas the REE-layers, although analogous to the Ca-based OD layer, has a p32 layer symmetry and thus their stacking does not lead to polytypism and OD phenomena.…”

Section: Introductionmentioning

confidence: 99%

Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths

et al. 2017

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Atomic-scale high angle annular dark field scanning transmission electron microscopy (HAADF STEM) imaging and electron diffractions are used to address the complexity of lattice-scale intergrowths of REE-fluorocarbonates from an occurrence adjacent to the Olympic Dam deposit, South Australia. The aims are to define the species present within the intergrowths and also assess the value of the HAADF STEM technique in resolving stacking sequences within mixed-layer compounds. Results provide insights into the definition of species and crystal-structural modularity. Lattice-scale intergrowths account for the compositional range between bastnäsite and parasite, as measured by electron probe microanalysis (at the µm-scale throughout the entire area of the intergrowths). These comprise rhythmic intervals of parisite and bastnäsite, or stacking sequences with gradational changes in the slab stacking between B, BBS and BS types (B-bastnäsite, S-synchysite). An additional occurrence of an unnamed B 2 S phase [CaCe 3 (CO 3 ) 4 F 3 ], up to 11 unit cells in width, is identified among sequences of parisite and bastnäsite within the studied lamellar intergrowths. Both B 2 S and associated parisite show hexagonal lattices, interpreted as 2H polytypes with c = 28 and 38 Å, respectively. 2H parisite is a new, short hexagonal polytype that can be added to the 14 previously reported polytypes (both hexagonal and rhombohedral) for this mineral. The correlation between satellite reflections and the number of layers along the stacking direction (c*) can be written empirically as: N sat = [(m × 2) + (n × 4)] − 1 for all B m S n compounds with S = 0. The present study shows intergrowths characterised by short-range stacking disorder and coherent changes in stacking along perpendicular directions. Knowing that the same compositional range can be expressed as long-period stacking compounds in the group, the present intergrowths are interpreted as being related to disequilibrium crystallisation followed by replacement. HAADF STEM imaging is found to be efficient for depiction of stacking sequences and their changes in mixed-layer compounds, particularly those in which heavy atoms, such as rare-earth elements, are essential components.

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Section: Introductionmentioning

confidence: 99%

Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths

et al. 2017

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“…7, the two stacking possibilities lead to non-equivalent pairs of adjacent layers. Such polytypes are said to be of the non-order-disorder (OD) type (Ferraris et al, 2008). Since every A n layer can contact in two ways to the adjacent A nþ1 layer, the (1) complexes can in principle be arranged to an infinity of different polytypes, which all belong to the same non-OD polytype family.…”

Section: Figurementioning

confidence: 99%

“…Polytypes are modular structures (Ferraris et al, 2008) that are composed of equivalent layers (or more generally rods or blocks) arranged into non-equivalent stackings. Polytypes, which are ubiquitous in all classes of materials, can crystallize with different degrees of order, ranging from perfectly ordered to purely random stackings.…”

Section: Introductionmentioning

confidence: 99%

Non-order–disorder allotwinning of the rhenium pincer complexcis-Re[(PNP^CH₂-iPr)(CO)₂Cl]

Glatz

Stöger

Kirchner

2017

Acta Crystallogr Sect B

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Crystals of cis-Re[(PNP CH 2 -iPr)(CO) 2 Cl] (1) are made up of two geometrically non-equivalent polytypes with respective symmetries of P2 1 /c and I2/a. The structures were determined in a concurrent refinement, taking into account overlap of diffraction spots. The polytypes are composed of layers with p x 12 1 /c1 symmetry and are of the non-order-disorder (OD) type (the layer interfaces are non-equivalent). Whereas the molecules of (1) differ in both polytypes, the Re atoms are located at nearly identical positions.

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“…A modular layer (ML) [52,53] is a sheet or plane of atoms organized in a regular 2D array. For closed-packed structures (CPSs), this is a hexagonal net.…”

Section: Chaotic Crystallographymentioning

confidence: 99%

Chaotic crystallography: how the physics of information reveals structural order in materials

Varn

Crutchfield

2015

Current Opinion in Chemical Engineering

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We review recent progress in applying information-and computation-theoretic measures to describe material structure that transcends previous methods based on exact geometric symmetries. We discuss the necessary theoretical background for this new toolset and show how the new techniques detect and describe novel material properties. We discuss how the approach relates to well known crystallographic practice and examine how it provides novel interpretations of familiar structures. Throughout, we concentrate on disordered materials that, while important, have received less attention both theoretically and experimentally than those with either periodic or aperiodic order.

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Crystallography of Modular Materials

Cited by 170 publications

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Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths

Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths

Non-order–disorder allotwinning of the rhenium pincer complexcis-Re[(PNP^CH₂-iPr)(CO)₂Cl]

Chaotic crystallography: how the physics of information reveals structural order in materials

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Crystallography of Modular Materials

Cited by 170 publications

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Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths

Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths

Non-order–disorder allotwinning of the rhenium pincer complexcis-Re[(PNPCH2-iPr)(CO)2Cl]

Chaotic crystallography: how the physics of information reveals structural order in materials

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Non-order–disorder allotwinning of the rhenium pincer complexcis-Re[(PNP^CH₂-iPr)(CO)₂Cl]