High–pressure GaAs Structure: AB_oI4_44_a_b

Picture of Structure; Click for Big Picture
Prototype : GaAs
AFLOW prototype label : AB_oI4_44_a_b
Strukturbericht designation : None
Pearson symbol : oI4
Space group number : 44
Space group symbol : $\mbox{Imm2}$
AFLOW prototype command : aflow --proto=AB_oI4_44_a_b
--params=
$a$,$b/a$,$c/a$,$z_{1}$,$z_{2}$


  • This is a high-pressure phase of GaAs, stable above 24 GPa. The experimental data used here was taken at a pressure of 28.1 GPa. Without loss of generality we can take $z_{1}=0$. When $a=b$ and $z_{2}=z_{1}+1/4$ this structure becomes the $\beta$–Sn (A5) structure.

Body-centered Orthorhombic primitive vectors:

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

Basis vectors:

\[ \begin{array}{ccccccc} & & \mbox{Lattice Coordinates} & & \mbox{Cartesian Coordinates} &\mbox{Wyckoff Position} & \mbox{Atom Type} \\ \mathbf{B}_{1} & =& z_{1} \, \mathbf{a}_{1} + z_{1} \, \mathbf{a}_{2}& =& z_{1} \, c \, \mathbf{\hat{z}}& \left(2a\right) & \mbox{As} \\ \mathbf{B}_{2} & =& \left(\frac12 + z_{2}\right) \, \mathbf{a}_{1}+ z_{2} \, \mathbf{a}_{2}+ \frac12 \, \mathbf{a}_{3}& =& \frac12 \, b \, \mathbf{\hat{y}}+ z_{2} \, c \, \mathbf{\hat{z}}& \left(2b\right) & \mbox{Ga} \\ \end{array} \]

References

  • S. T. Weir, Y. K. Vohra, C. A. Vanderborgh, and A. L. Ruoff, Structural phase transitions in GaAs to 108 GPa, Phys. Rev. B 39, 1280–1285 (1989), doi:10.1103/PhysRevB.39.1280.

Found in

  • P. Villars and L. Calvert, Pearson's Handbook of Crystallographic Data for Intermetallic Phases (ASM International, Materials Park, OH, 1991), 2nd edn., pp. 1135.

Geometry files


Prototype Generator

aflow --proto=AB_oI4_44_a_b --params=

Species:

Running:

Output: