Fe8N ($D2_{g}$) Structure : A8B_tI18_139_deh_a

Picture of Structure; Click for Big Picture
Prototype : Fe8N
AFLOW prototype label : A8B_tI18_139_deh_a
Strukturbericht designation : $D2_{g}$
Pearson symbol : tI18
Space group number : 139
Space group symbol : $I4/mmm$
AFLOW prototype command : aflow --proto=A8B_tI18_139_deh_a
--params=
$a$,$c/a$,$z_{3}$,$x_{4}$


  • (Jack, 1951) and others refer to this structure as $\alpha$$$–Fe$_{16}$N$_{2}$.
  • (Yamashita, 2012) determined the structure by examining crystals containing various amounts of $\alpha$$$–Fe$_{16}$N$_{2}$ and $\alpha$–Fe (bcc iron). We use their data from the sample that was 90% $\alpha$$$–Fe$_{16}$N$_{2}$. Their measurements were confirmed by first principles calculations, and are in agreement with the first principles calculations of (Sims, 2012).

Body-centered Tetragonal primitive vectors:

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

Basis vectors:

\[ \begin{array}{ccccccc} & & \mbox{Lattice Coordinates} & & \mbox{Cartesian Coordinates} &\mbox{Wyckoff Position} & \mbox{Atom Type} \\ \mathbf{B}_{1} & = & 0 \, \mathbf{a}_{1} + 0 \, \mathbf{a}_{2} + 0 \, \mathbf{a}_{3} & = & 0 \, \mathbf{\hat{x}} + 0 \, \mathbf{\hat{y}} + 0 \, \mathbf{\hat{z}} & \left(2a\right) & \mbox{N} \\ \mathbf{B}_{2} & = & \frac{3}{4} \, \mathbf{a}_{1} + \frac{1}{4} \, \mathbf{a}_{2} + \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{2}a \, \mathbf{\hat{y}} + \frac{1}{4}c \, \mathbf{\hat{z}} & \left(4d\right) & \mbox{Fe I} \\ \mathbf{B}_{3} & = & \frac{1}{4} \, \mathbf{a}_{1} + \frac{3}{4} \, \mathbf{a}_{2} + \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{2}a \, \mathbf{\hat{x}} + \frac{1}{4}c \, \mathbf{\hat{z}} & \left(4d\right) & \mbox{Fe I} \\ \mathbf{B}_{4} & = & z_{3} \, \mathbf{a}_{1} + z_{3} \, \mathbf{a}_{2} & = & z_{3}c \, \mathbf{\hat{z}} & \left(4e\right) & \mbox{Fe II} \\ \mathbf{B}_{5} & = & -z_{3} \, \mathbf{a}_{1}-z_{3} \, \mathbf{a}_{2} & = & -z_{3}c \, \mathbf{\hat{z}} & \left(4e\right) & \mbox{Fe II} \\ \mathbf{B}_{6} & = & x_{4} \, \mathbf{a}_{1} + x_{4} \, \mathbf{a}_{2} + 2x_{4} \, \mathbf{a}_{3} & = & x_{4}a \, \mathbf{\hat{x}} + x_{4}a \, \mathbf{\hat{y}} & \left(8h\right) & \mbox{Fe III} \\ \mathbf{B}_{7} & = & -x_{4} \, \mathbf{a}_{1}-x_{4} \, \mathbf{a}_{2}-2x_{4} \, \mathbf{a}_{3} & = & -x_{4}a \, \mathbf{\hat{x}}-x_{4}a \, \mathbf{\hat{y}} & \left(8h\right) & \mbox{Fe III} \\ \mathbf{B}_{8} & = & x_{4} \, \mathbf{a}_{1}-x_{4} \, \mathbf{a}_{2} & = & -x_{4}a \, \mathbf{\hat{x}} + x_{4}a \, \mathbf{\hat{y}} & \left(8h\right) & \mbox{Fe III} \\ \mathbf{B}_{9} & = & -x_{4} \, \mathbf{a}_{1} + x_{4} \, \mathbf{a}_{2} & = & x_{4}a \, \mathbf{\hat{x}}-x_{4}a \, \mathbf{\hat{y}} & \left(8h\right) & \mbox{Fe III} \\ \end{array} \]

References

  • S. Yamashita, Y. Masubuchi, Y. Nakazawa, T. Okayama, M. Tsuchiya, and S. Kikkawa, Crystal structure and magnetic properties of $\alpha$$$–Fe$_16$N$_2$ containing reisdual $\alpha$–Fe prepared by low–temperature ammonia nitridation, J. Solid State Chem. 194, 76–79 (2012), doi:10.1016/j.jssc.2012.07.025.
  • K. H. Jack, The occurrence and the crystal structure of $\alpha$$$–iron nitride; a new type of interstitial alloy formed during the tempering of nitrogen–martensite, Proc. Roy. Soc. Lond. A 208, 216–224 (1951), doi:10.1098/rspa.1951.0155.
  • H. Sims, W. H. Butler, M. Richter, K. Koepernik, E. \cSa\cs\io\vglu, C. Friedrich, and S. Blügel, Theoretical investigation into the possibility of very large moments in Fe16N2, Phys. Rev. B 86, 174422 (2012), doi:10.1103/PhysRevB.86.174422.

Geometry files


Prototype Generator

aflow --proto=A8B_tI18_139_deh_a --params=

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