Anisotropic thermal expansion of the acetylene–ammonia co-crystal under Titan's conditions

Vu, Tuan; Maynard-Casely, Helen E.; Cable, Morgan L.; Hodyss, Robert; Choukroun, Mathieu; Malaska, Michael J.

doi:10.1107/s1600576720014028

Cited by 7 publications

(3 citation statements)

References 47 publications

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“…Thus, the expansion can be expected to be the most pronounced in that direction. Similar anisotropy has been reported for a number of organic solids and cocrystals under cryogenic conditions, − suggesting that this may be quite common among putative Titan materials.…”

Section: Resultssupporting

confidence: 75%

1,3-Butadiene on Titan: Crystal Structure, Thermal Expansivity, and Raman Signatures

Maynard-Casely

Cable

et al. 2022

ACS Earth Space Chem.

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Titan is one of the most Earth-like objects in the Solar System, hosting a nitrogen-rich atmosphere and an impressive inventory of organics ranging from simple to complex. 1,3-Butadiene has been suggested to be one of the photochemical products that could be present on Titan's surface. As the simplest conjugated hydrocarbon, it is expected to partake in many chemical processes that influence Titan's geology and evolution. However, the crystal structure and thermal expansivity of 1,3-butadiene, two of its most fundamental properties, have remained largely unknown for over eight decades, especially at cryogenic conditions often encountered on planetary bodies. In this work, a series of powder X-ray diffraction and micro-Raman experiments have been conducted in order to elucidate the crystal structure and thermal behavior of solid 1,3-butadiene between 85 and 165 K. Specifically, a single crystalline phase (space group P2 1 /c) is observed in the temperature range of study in which the butadiene molecules form layers of zigzag chains that are stabilized by an intricate network of intermolecular C−H•••π interactions. This monoclinic structure is shown to exhibit significant anisotropic thermal expansion along the three directions with the majority occurring along the crystallographic b-axis. The calculated bulk density of 1,3-butadiene (0.877 g/cm 3 at 150 K) is considerably lower than previously realized. These results help enhance our understanding of the putative molecular solids that make up Titan's surface and could hold important implications for physical as well as mechanical processes occurring on this icy satellite.

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Section: Resultssupporting

confidence: 75%

1,3-Butadiene on Titan: Crystal Structure, Thermal Expansivity, and Raman Signatures

Maynard-Casely

Cable

et al. 2022

ACS Earth Space Chem.

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“…In contrast, the structures of acetonitrile:acetylene (1:2) and acetylene:ammonia (1:1) show distinct layering, with the majority of the intermolecular interactions restricted to two dimensions. Diffraction studies (and other analysis) have established that both of these co-crystals would be stable under Titan conditions, ,, and as discussed below, this layering has an impact on their thermal expansion behavior.…”

Section: Diffraction Studiesmentioning

confidence: 95%

Titan in a Test Tube: Organic Co-crystals and Implications for Titan Mineralogy

et al. 2021

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Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS: In this Account, we highlight recent work in the developing field of mineralogy of Saturn's moon Titan, focusing on binary co-crystals of small organic molecules. Titan has a massive inventory of organic molecules on its surface that are formed via photochemistry in the atmosphere and likely processing on the surface as well. Physical processes both in the atmosphere and on the surface can lead to molecules interacting at cryogenic temperatures. Recent laboratory work has demonstrated that cocrystals between two or more molecules can form under these conditions. In the organic-rich environment of Titan, such cocrystals are naturally occurring minerals and a critical area of research to understand the physical, chemical, and possibly even biological and prebiotic processes occurring in this alien world. With a future NASA mission, Dragonf ly, slated to land on Titan in the next decade, much work is needed to understand organic mineralogy in order to properly interpret the data from this and past Titan missions, such as Cassini-Huygens. By cataloging Titan minerals and their properties, we can begin to connect these behaviors to large-scale surface features observed on Titan (labyrinth terrain, lake evaporites, karst, dunes, etc.), and possible processes leading to their formation (erosion, deposition, etc.). To date, seven co-crystals (aside from clathrates and hydrates) have been experimentally reported to form under Titan-relevant conditions, with an eighth predicted by theoretical modeling. This Account will summarize the formation and properties of these cryominerals and discuss the implications for surface processes on Titan. Enhanced thermal expansion and decreased crystal size, for example, may lead to fracturing and/or more rapid erosion of co-crystal-based deposits; density changes upon co-crystal formation may also play a role in organic diagenesis and metamorphism on Titan. Some cryominerals with stability only under certain conditions may preserve the evidence of Titan's history, such as cryovolcanic activity, ethane fluvial/pluvial exposure, and outgassing of CO 2 from the interior of the moon.In this Account, we will also highlight areas of future work, such as the characterization of pure molecular solids and the search for ternary (and more complex) co-crystals. We note that on Titan, organic chemistry dominates, which gives a unique opportunity for chemists to play an even more significant role in planetary science discoveries and likewise in discoveries motivated by planetary science to inform fundamental organic and physical chemistry research.

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“…4), most likely caused by deposition of the sample primarily on the inner walls of the capillary. The patterns were subsequently analyzed to determine the thermal expansion of the co-crystal under Titan surface and subsurface conditions (Vu, Maynard-Casely et al, 2020).…”

Section: Example: Acetylene-ammonia Co-crystalmentioning

confidence: 99%

A simple gas introduction system for cryogenic powder X-ray diffraction

Hodyss

Choukroun

et al. 2021

J Appl Cryst

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A simple system is described for the introduction of gases into standard X-ray diffraction capillaries mounted in situ in the X-ray beam of laboratory X-ray diffraction instruments. This system retains many of the advantages of the standard Norby cell, but does not require custom machining and has less stringent space restrictions. The system has been used to study the crystallization and interaction of volatile organics at cryogenic temperatures, but gas–solid interactions could also be studied at elevated temperatures using this approach.

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Anisotropic thermal expansion of the acetylene–ammonia co-crystal under Titan's conditions

Cited by 7 publications

References 47 publications

1,3-Butadiene on Titan: Crystal Structure, Thermal Expansivity, and Raman Signatures

1,3-Butadiene on Titan: Crystal Structure, Thermal Expansivity, and Raman Signatures

Titan in a Test Tube: Organic Co-crystals and Implications for Titan Mineralogy

A simple gas introduction system for cryogenic powder X-ray diffraction

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