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. 2014 Jul 22;111(29):10456-61.
doi: 10.1073/pnas.1410690111. Epub 2014 Jul 7.

Crystal structure and encapsulation dynamics of ice II-structured neon hydrate

Xiaohui Yu  1 , Jinlong Zhu  2 , Shiyu Du  3 , Hongwu Xu  4 , Sven C Vogel  5 , Jiantao Han  5 , Timothy C Germann  6 , Jianzhong Zhang  5 , Changqing Jin  7 , Joseph S Francisco  8 , Yusheng Zhao  2
Affiliations

Crystal structure and encapsulation dynamics of ice II-structured neon hydrate

Xiaohui Yu et al. Proc Natl Acad Sci U S A. .

Abstract

Neon hydrate was synthesized and studied by in situ neutron diffraction at 480 MPa and temperatures ranging from 260 to 70 K. For the first time to our knowledge, we demonstrate that neon atoms can be enclathrated in water molecules to form ice II-structured hydrates. The guest Ne atoms occupy the centers of D2O channels and have substantial freedom of movement owing to the lack of direct bonding between guest molecules and host lattices. Molecular dynamics simulation confirms that the resolved structure where Ne dissolved in ice II is thermodynamically stable at 480 MPa and 260 K. The density distributions indicate that the vibration of Ne atoms is mainly in planes perpendicular to D2O channels, whereas their distributions along the channels are further constrained by interactions between adjacent Ne atoms.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Rietveld refinement of neutron diffraction data obtained for Ne clathrate hydrate at 480 MPa and 70 K. The observed intensities and calculated pattern are represented, respectively, by circles and a red solid line, and the difference curve is shown below in blue. The tick marks denote the positions of allowed Bragg reflections. All Al peaks from the pressure cell are excluded.
Fig. 2.
Fig. 2.
Temperature dependence of cell parameters of Ne hydrate at 480 MPa (A, volume; B, lattice parameters a and c). The data for pure ice II (11) and He hydrate (5) at 480 MPa and 200 K are also presented for comparison.
Fig. 3.
Fig. 3.
(A) The difference Fourier nuclear density map without Ne atoms in ice cages shows that the incorporated Ne atoms occupy the center of D2O channels. The isosurface is at 7 fm/Å3, as shown by the yellow surface. The red dots, which represents higher density of the isosurface, are the intersection of the yellow ball with the cutoff of the unit cell along the (001) plane. The red, white, and purple balls represent O, H, and Ne atoms, respectively (B and C). The D–O bonds within the D2O molecule are represented by solid white lines; the hydrogen bonds that connect different D2O molecules are represented by dashed green lines. (B) A top view of the refined crystal structure for Ne hydrate (c direction). (C) A side view of the refined crystal structure for Ne hydrate. D1–O1–D2 are water molecules in the puckered ring. D1s connect the ring inside and D2s connect the adjacent flat ring. D3–O2–D4 are water molecules in the flat ring. D3s connect the ring inside and D4s connect different channels.
Fig. 4.
Fig. 4.
(A) A snapshot of Ne hydrate structure at 480 MPa and 260 K from MD simulation (top view from c direction). (B) The Ne occupancy change with temperature refined from neutron diffraction patterns.
Fig. 5.
Fig. 5.
(A) Projection of Ne local density distribution (×103) in a single hydrate cage on the a–c (x–z) plane. (B) Projection of Ne global density distribution on the a–b (x–y) plane. (C) Projection of Ne global density distribution on the a-c (x–z) plane. The units in A, B, and C are angstroms. (D) The vibration of Ne atoms in D2O cages refined from neutron diffraction patterns at selected temperatures.
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References

    1. Sloan ED., Jr . Clathrate Hydrates of Natural Gases. 2nd Ed. New York: Dekker; 1998.
    1. Itohaand H, Tse JS, Kawamura K. The structure and dynamics of doubly occupied Ar hydrate. J Chem Phys. 2001;115(20):9414–9420.
    1. Tse JS, et al. Anharmonic motions of Kr in the clathrate hydrate. Nat Mater. 2005;4(12):917–921. - PubMed
    1. Sanloup C, Mao Hk HK, Hemley RJ. High-pressure transformations in xenon hydrates. Proc Natl Acad Sci USA. 2002;99(1):25–28. - PMC - PubMed
    1. Londono D, Kuhs V, Finney JL. Enclathration of helium in ice II: The first helium hydrate. Nature. 1988;332:141–142.

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