NH4HgCl3 ($E2_{5}$) Structure : A3BC_tP5_123_cg_a_d

Picture of Structure; Click for Big Picture
Prototype : Cl3Hg(NH4)
AFLOW prototype label : A3BC_tP5_123_cg_a_d
Strukturbericht designation : $E2_{5}$
Pearson symbol : tP5
Space group number : 123
Space group symbol : $P4/mmm$
AFLOW prototype command : aflow --proto=A3BC_tP5_123_cg_a_d
--params=
$a$,$c/a$,$z_{4}$


  • The positions of the hydrogen atoms in the NH4 ion are not given, so we only provide the nitrogen positions (labeled as NH4). It is likely that the hydrogen atoms are freely rotating around the nitrogen, as any reasonable fixed positions would destroy both the inversion symmetry and the four–fold rotation axis exhibited by space group $P4/mmm$.
  • (Harmsen, 1939) and (Herrmann, 1943) give multiple possible space groups for this structure. We have chosen the highest symmetry representation, space group $P4/mmm$ #123.

Simple Tetragonal primitive vectors:

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

Basis vectors:

\[ \begin{array}{ccccccc} & & \mbox{Lattice Coordinates} & & \mbox{Cartesian Coordinates} &\mbox{Wyckoff Position} & \mbox{Atom Type} \\ \mathbf{B}_{1} & = & 0 \, \mathbf{a}_{1} + 0 \, \mathbf{a}_{2} + 0 \, \mathbf{a}_{3} & = & 0 \, \mathbf{\hat{x}} + 0 \, \mathbf{\hat{y}} + 0 \, \mathbf{\hat{z}} & \left(1a\right) & \mbox{Hg} \\ \mathbf{B}_{2} & = & \frac{1}{2} \, \mathbf{a}_{1} + \frac{1}{2} \, \mathbf{a}_{2} & = & \frac{1}{2}a \, \mathbf{\hat{x}} + \frac{1}{2}a \, \mathbf{\hat{y}} & \left(1c\right) & \mbox{Cl I} \\ \mathbf{B}_{3} & = & \frac{1}{2} \, \mathbf{a}_{1} + \frac{1}{2} \, \mathbf{a}_{2} + \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{2}a \, \mathbf{\hat{x}} + \frac{1}{2}a \, \mathbf{\hat{y}} + \frac{1}{2}c \, \mathbf{\hat{z}} & \left(1d\right) & \mbox{NH$_{4}$} \\ \mathbf{B}_{4} & = & z_{4} \, \mathbf{a}_{3} & = & z_{4}c \, \mathbf{\hat{z}} & \left(2g\right) & \mbox{Cl II} \\ \mathbf{B}_{5} & = & -z_{4} \, \mathbf{a}_{3} & = & -z_{4}c \, \mathbf{\hat{z}} & \left(2g\right) & \mbox{Cl II} \\ \end{array} \]

References

  • E. J. Harmsen, The Crystal Structure of NH4HgCl3, Zeitschrift für Kristallographie – Crystalline Materials 100, 208–211 (1939), doi:10.1524/zkri.1939.100.1.208.

Found in

  • K. Herrmann, ed., Strukturbericht Band VII 1939 (Akademische Verlagsgesellschaft M. B. H., Leipzig, 1943).

Geometry files


Prototype Generator

aflow --proto=A3BC_tP5_123_cg_a_d --params=

Species:

Running:

Output: