Structure of Crystals: Creation Date: 18 Nov 2015 Last Modified: 17 Feb 2016

# The High Presssure H3S Structure

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

• Prototype: H3S
• AFLOW Prototype: None
• Pearson Symbol: cI8
• Strukturbericht Designation: None
• Space Group: Im3m
• Number: 229
• Reference: (Duan, 2014)
• Other Compounds with this Structure: La2O3, Nd2O3
In both cases the Oxygen atoms only partially occupy the (6b) Wyckoff positions

Body-centered Cubic Primitive Vectors:

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

Basis Vectors:

$\begin{array}{ccccccc} & & \mbox{Lattice Coordinates} & & \mbox{Cartesian Coordinates} & \mbox{Wyckoff Position} & \mbox{Atom Type} \\ \vec{B_{1}} & = & 0 & = & 0 & (2a) & \mbox{S} \\ \vec{B_{2}} & = & \frac12 \, \vec{a_2} + \frac12 \, \vec{a_3} & = & \frac12 \, a \, \hat{x} & (6b) & \mbox{H} \\ \vec{B_{3}} & = & \frac12 \, \vec{a_1} + \frac12 \, \vec{a_3} & = & \frac12 \, a \, \hat{y} & (6b) & \mbox{H} \\ \vec{B_{4}} & = & \frac12 \, \vec{a_1} + \frac12 \, \vec{a_2} & = & \frac12 \, a \, \hat{z} & (6b) & \mbox{H} \\ \end{array}$