Why Are Some Crystals Straight?

Li, Chao; Shtukenberg, Alexander G.; Vogt-Maranto, Leslie; Efrati, Efi; Raiteri, Paolo; Gale, Julian D.; Rohl, Andrew L.; Kahr, Bart

doi:10.1021/acs.jpcc.0c04258

Cited by 35 publications

(50 citation statements)

References 84 publications

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“…Nonetheless, more than a quarter of organic compounds can form twisted molecular crystals. [8,10] The early efforts to understand the origin of the twist in these exotic structure sought external mechanisms that act on the unbalanced growing faces of the crystals and distort the crystal into a helical form either elastically or plastically by locking into its structure chiral defects. [18] The path we adopt here is very different, assuming that the twist originates from the constituents and their relative interactions.…”

Section: Discussionmentioning

confidence: 99%

“…Continuous helical symmetry with a finite pitch is incompatible with translational symmetry. Nonetheless, more than a quarter of organic compounds can form twisted molecular crystals [8,10] . The early efforts to understand the origin of the twist in these exotic structure sought external mechanisms that act on the unbalanced growing faces of the crystals and distort the crystal into a helical form either elastically or plastically by locking into its structure chiral defects [18] .…”

Section: Discussionmentioning

confidence: 99%

“…In recent years Berenauer's discovery was revisited and studied using modern tools. [9][10][11][12] Electron microscopy revealed twisted molecular crystals were narrow needle-like structures characterized by smooth facets, and a twist rate that decreased as their cross-sections grew, and selected area electron diffraction showed sharp peaks, as one would expect for regular crystals.…”

Section: Introductionmentioning

confidence: 86%

“…In 1929 German mineralogist Ferdinand Bernauer published a monograph titled “Gedrillte” Kristalle (Twisted Crystals), [8] where he claimed that over 25 % of small organic compounds could crystalize to form mesoscale helical structures. In recent years Berenauer's discovery was revisited and studied using modern tools [9–12] . Electron microscopy revealed twisted molecular crystals were narrow needle‐like structures characterized by smooth facets, and a twist rate that decreased as their cross‐sections grew, and selected area electron diffraction showed sharp peaks, as one would expect for regular crystals.…”

Section: Introductionmentioning

confidence: 99%

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Geometric Frustration in Molecular Crystals

Efrati

2020

Israel Journal of Chemistry

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Unlike Lego bricks that perfectly assemble next to one another, solid assemblies of organic compounds often include some inevitable misfit between constituents, giving rise to geometric frustration. In order to fit into the assembly the molecular building blocks must distort, at some finite energetic cost. In cases where this distortion at the ground state is uniform across all the units in the assembly, the associated geometric frustration is said to be locally resolved. Such locally resolved frustration carries little implications on the morphology and response properties of the assembled structure. However, in many cases, for small enough assemblies there are non-local compromises that are more energetically favorable. These conformations are associated with non-uniform distortions and highly cooperative response between the molecular constituents. The cooperative nature of frustrated assemblies may result in growth arrest, tendency to form filaments, exotic response properties and large morphological variations during the growth of the assembly.Almost a century ago German mineralogist Ferdinand Bernauer discovered that a large fraction of small organic compounds could form twisted molecular crystals. These are straight and narrow needle-like structures with mesoscopic pitch, a crystalographically impossible structure. Recent revived interest in twisted molecular crystals discovered even more compounds that form these exotic assemblies and led to their study by modern means. Electron microscopy revealed straight faceted structures with sharp diffraction peaks in selected area electron diffraction, much like regular crystals. Moreover, the pitch of the molecular crystals varied with size, with thicker crystals exhibiting less twist. In this work we review twisted molecular crystals as frustrated assemblies. In this approach twist emerges from the preferred morphology at the constituent scale, and gets attenuated with size by the incompatibility of twist and largescale crystalline order. We discuss two distinct mechanisms that produce twisted molecular crystals, and provide a prediction for the twist decay as a function of the crystals' spatial dimensions.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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Geometric Frustration in Molecular Crystals

Efrati

2020

Israel Journal of Chemistry

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“…Simulations of the nanocrystals of benzil suggest twisting and therefore that they do not have a habitual crystallographic lattice. [115] The model then simulated the effects of introducing screw dislocations that went in the same sense as the helical twist, or against it. When screw dislocations were introduced in a positive or negative sense, for a given enantiomorph these would tend to twist further or to straighten the object, and this latter case was referred to as Eshelby untwisting.…”

Section: Making Twisted Crystalsmentioning

confidence: 99%

Stereochemistry and Twisted Crystals

Killalea

Amabilino

2021

Israel Journal of Chemistry

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Charge Transport in Twisted Organic Semiconductor Crystals of Modulated Pitch

et al. 2022

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Many molecular crystals (approximately one third) grow as twisted helicoidal ribbons from the melt, and this preponderance is even higher in restricted classes of materials, for instance charge transfer complexes. Previously, twisted crystallites of such complexes present an increase in carrier mobilities. Here, the effect of twisting on charge mobility is better analyzed for a mono-component organic semiconductor 2 2,5-bis(3-dodecyl-2-thienyl)-thiazolo [5,4-d]thiazole (BDT) that forms twisted crystals with varied helicoidal pitches and makes a possible correlation with carrier mobility. These films were analyzed by Xray scattering and Mueller matrix polarimetry to characterize the microscale organization of the polycrystalline ensembles. Carrier mobilities of organic field effect transistors were five times higher when the crystals were grown with the smallest pitches (most twisted) compared to those with the largest pitches along the fiber elongation direction. A ten-fold increase was observed along the perpendicular direction.Simulation of electrical potential based on scanning electron micrographs and density functional theory suggests that the twisting-enhanced mobility is mainly controlled by the fiber organization in the film. A greater number of tightly packed twisted fibers separated by numerous smaller gaps permits better charge transport over the film surface compared to fewer big crystallites separated by larger gaps.

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Why Are Some Crystals Straight?

Cited by 35 publications

References 84 publications

Geometric Frustration in Molecular Crystals

Geometric Frustration in Molecular Crystals

Stereochemistry and Twisted Crystals

Charge Transport in Twisted Organic Semiconductor Crystals of Modulated Pitch

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