Encyclopedia of Crystallographic Prototypes

AFLOW Prototype: A3B_cI8_229_b_a

  • M. J. Mehl, D. Hicks, C. Toher, O. Levy, R. M. Hanson, G. L. W. Hart, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 1, Comp. Mat. Sci. 136, S1-S828 (2017). (doi=10.1016/j.commatsci.2017.01.017)
  • D. Hicks, M. J. Mehl, E. Gossett, C. Toher, O. Levy, R. M. Hanson, G. L. W. Hart, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 2, Comp. Mat. Sci. 161, S1-S1011 (2019). (doi=10.1016/j.commatsci.2018.10.043)
  • D. Hicks, M.J. Mehl, M. Esters, C. Oses, O. Levy, G.L.W. Hart, C. Toher, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 3, Comp. Mat. Sci. 199, 110450 (2021). (doi=10.1016/j.commatsci.2021.110450)

High–pressure H3S Structure: A3B_cI8_229_b_a

Picture of Structure; Click for Big Picture
Prototype : H3S
AFLOW prototype label : A3B_cI8_229_b_a
Strukturbericht designation : None
Pearson symbol : cI8
Space group number : 229
Space group symbol : $\text{Im}\bar{3}\text{m}$
AFLOW prototype command : aflow --proto=A3B_cI8_229_b_a
--params=
$a$


Other compounds with this structure

  • La2O3, Nd2O3 (In both cases the oxygen atoms only partially occupy the (6b) Wyckoff positions.)

  • (Duan, 2014) predicted that this structure of H3S would be a conventional superconductor at temperatures above 191 K and a pressure of 200 GPa. (Drozdov, 2015) found a superconductor in the hydrogen-sulfur system at 203 K and pressure near 200 GPa. (Bernstein, 2015) showed that this structure is the ground state of the H–S system near 200 GPa. Both La2O3 and Nd2O3 can form in this structure under ambient conditions, but in both cases the oxygen atoms occupy only 50% of the (6b) Wyckoff positions. We have used the fact that all vectors of the form $\left( \pm a/2 \mathbf{\hat{x}} \pm a/2 \mathbf{\hat{y}} \pm a/2 \mathbf{\hat{z}} \right)$ are primitive vectors of the body-centered cubic lattice to simplify the positions of some atoms in both lattice and Cartesian coordinates.

Body-centered Cubic primitive vectors:

\[ \begin{array}{ccc} \mathbf{a}_1 & = & - \frac12 \, a \, \mathbf{\hat{x}} + \frac12 \, a \, \mathbf{\hat{y}} + \frac12 \, a \, \mathbf{\hat{z}} \\ \mathbf{a}_2 & = & ~ \frac12 \, a \, \mathbf{\hat{x}} - \frac12 \, a \, \mathbf{\hat{y}} + \frac12 \, a \, \mathbf{\hat{z}} \\ \mathbf{a}_3 & = & ~ \frac12 \, a \, \mathbf{\hat{x}} + \frac12 \, a \, \mathbf{\hat{y}} - \frac12 \, a \, \mathbf{\hat{z}} \\ \end{array} \]

Basis vectors:

\[ \begin{array}{ccccccc} & & \text{Lattice Coordinates} & & \text{Cartesian Coordinates} &\text{Wyckoff Position} & \text{Atom Type} \\ \mathbf{B}_{1} & = &0 \, \mathbf{a}_{1} + 0 \, \mathbf{a}_{2} + 0 \, \mathbf{a}_{3} & = &0 \mathbf{\hat{x}} + 0 \mathbf{\hat{y}} + 0 \mathbf{\hat{z}} & \left(2a\right) & \text{S} \\ \mathbf{B}_{2} & = &\frac12 \, \mathbf{a}_{2}+ \frac12 \, \mathbf{a}_{3}& = &\frac12 \, a \, \mathbf{\hat{x}}& \left(6b\right) & \text{H} \\ \mathbf{B}_{3} & = &\frac12 \, \mathbf{a}_{1}+ \frac12 \, \mathbf{a}_{3}& = &\frac12 \, a \, \mathbf{\hat{y}}& \left(6b\right) & \text{H} \\ \mathbf{B}_{4} & = &\frac12 \, \mathbf{a}_{1}+ \frac12 \, \mathbf{a}_{2}& = &\frac12 \, a \, \mathbf{\hat{z}}& \left(6b\right) & \text{H} \\ \end{array} \]

References

  • A. P. Drozdov, M. I. Eremets, I. A. Troyan, V. Ksenofontov, and S. I. Shylin, Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system, Nature 525, 73–76 (2015), doi:10.1038/nature14964.
  • D. Duan, Y. Liu, F. Tian, D. Li, X. Huang, Z. Zhao, H. Yu, B. Liu, W. Tian, and T. Cui, Pressure–induced metallization of dense (H2S)2H2 with high–Tc superconductivity, Sci. Rep. 4, 6968 (2014), doi:10.1038/srep06968.
  • N. Bernstein, C. Stephen Hellberg, M. D. Johannes, I. I. Mazin, and M. J. Mehl, What superconducts in sulfur hydrides under pressure and why, Phys. Rev. B 91, 060511(R) (2015), doi:10.1103/PhysRevB.91.060511.

Geometry files


Prototype Generator

aflow --proto=A3B_cI8_229_b_a --params=

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