## NH$_{4}$HgCl$_{3}$ ($E2_{5}$) Structure: A3BC_tP5_123_ah_c_b-001

 Prototype Cl$_{3}$H$_{4}$HgN$_{4}$ AFLOW prototype label A3BC_tP5_123_ah_c_b-001 Strukturbericht designation $E2_{5}$ ICSD 15962 Pearson symbol tP5 Space group number 123 Space group symbol $P4/mmm$ AFLOW prototype command aflow --proto=A3BC_tP5_123_ah_c_b-001 --params=$a, \allowbreak c/a, \allowbreak z_{4}$

• The positions of the hydrogen atoms are not given. 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 $P4/mmm$ #123.
• (Harmsen, 1939) and (Herrmann, 1943) give multiple possible space groups for this structure. We have chosen the highest symmetry representation, space group $P4/mmm$.

### 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

Lattice coordinates Cartesian coordinates Wyckoff position Atom type
$\mathbf{B_{1}}$ = $0$ = $0$ (1a) Cl I
$\mathbf{B_{2}}$ = $\frac{1}{2} \, \mathbf{a}_{3}$ = $\frac{1}{2}c \,\mathbf{\hat{z}}$ (1b) NH I
$\mathbf{B_{3}}$ = $\frac{1}{2} \, \mathbf{a}_{1}+\frac{1}{2} \, \mathbf{a}_{2}$ = $\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}$ (1c) Hg I
$\mathbf{B_{4}}$ = $\frac{1}{2} \, \mathbf{a}_{1}+\frac{1}{2} \, \mathbf{a}_{2}+z_{4} \, \mathbf{a}_{3}$ = $\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}+c z_{4} \,\mathbf{\hat{z}}$ (2h) Cl II
$\mathbf{B_{5}}$ = $\frac{1}{2} \, \mathbf{a}_{1}+\frac{1}{2} \, \mathbf{a}_{2}- z_{4} \, \mathbf{a}_{3}$ = $\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}- c z_{4} \,\mathbf{\hat{z}}$ (2h) Cl II

### Found in

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

### Prototype Generator

aflow --proto=A3BC_tP5_123_ah_c_b --params=$a,c/a,z_{4}$