Orange (averaged) HgI$_{2}$ Structure: AB2_tP12_115_j_egi-001
| Prototype | HgI$_{2}$ |
| AFLOW prototype label | AB2_tP12_115_j_egi-001 |
| ICSD | none |
| Pearson symbol | tP12 |
| Space group number | 115 |
| Space group symbol | $P\overline{4}m2$ |
| AFLOW prototype command |
aflow --proto=AB2_tP12_115_j_egi-001
--params=$a, \allowbreak c/a, \allowbreak z_{1}, \allowbreak z_{2}, \allowbreak x_{3}, \allowbreak x_{4}, \allowbreak z_{4}$ |
- HgI$_{2}$ can be found in a variety of forms (Gumiński, 1997):
- The ground state, coccinite, also known as red or $\alpha$–HgI$_{2}$ and given the Strukturbericht designation $C13$. It is stable up to 135$^\circ$C.
- At higher temperatures this transforms into yellow or $\beta$–HgI$_{2}$ in the HgBr$_{2}$ ($C24$) structure. This is stable up to the melting point at 258$^\circ$C.
- (Schwarzenbach, 1969) studied the metastable orange HgI$_{2}$ body-centered tetragonal ($I4_{1}/amd$ #141) phase. This structure was refined by (Hostettler, 2002).
- (Hostettler, 2002) also found a second orange HgI$_{2}$ phase in a simple tetragonal ($P4_{2}/nmc$ #137) cell.
- The last two structures differ by stacking order. (Hostettler, 2002) used them to produce an averaged orange HgI$_{2}$ structure (this structure), space group $P\overline{4}m2$ #115.
- This structure is an
average
of the Orange I and Orange II structures. The averaging procedure places the iodine I atoms only 0.36Å apart, so this is not a physical structure. We retain it as an example of a structure in space group $P\overline{4}m2$ #115.
\[ \begin{array}{ccc}
\mathbf{a_{1}}&=&a \,\mathbf{\hat{x}}\\\mathbf{a_{2}}&=&a \,\mathbf{\hat{y}}\\\mathbf{a_{3}}&=&c \,\mathbf{\hat{z}}
\end{array}\]
Basis vectors
| Lattice coordinates | Cartesian coordinates | Wyckoff position | Atom type | |||
|---|---|---|---|---|---|---|
| $\mathbf{B_{1}}$ | = | $z_{1} \, \mathbf{a}_{3}$ | = | $c z_{1} \,\mathbf{\hat{z}}$ | (2e) | I I |
| $\mathbf{B_{2}}$ | = | $- z_{1} \, \mathbf{a}_{3}$ | = | $- c z_{1} \,\mathbf{\hat{z}}$ | (2e) | I I |
| $\mathbf{B_{3}}$ | = | $\frac{1}{2} \, \mathbf{a}_{2}+z_{2} \, \mathbf{a}_{3}$ | = | $\frac{1}{2}a \,\mathbf{\hat{y}}+c z_{2} \,\mathbf{\hat{z}}$ | (2g) | I II |
| $\mathbf{B_{4}}$ | = | $\frac{1}{2} \, \mathbf{a}_{1}- z_{2} \, \mathbf{a}_{3}$ | = | $\frac{1}{2}a \,\mathbf{\hat{x}}- c z_{2} \,\mathbf{\hat{z}}$ | (2g) | I II |
| $\mathbf{B_{5}}$ | = | $x_{3} \, \mathbf{a}_{1}+x_{3} \, \mathbf{a}_{2}+\frac{1}{2} \, \mathbf{a}_{3}$ | = | $a x_{3} \,\mathbf{\hat{x}}+a x_{3} \,\mathbf{\hat{y}}+\frac{1}{2}c \,\mathbf{\hat{z}}$ | (4i) | I III |
| $\mathbf{B_{6}}$ | = | $- x_{3} \, \mathbf{a}_{1}- x_{3} \, \mathbf{a}_{2}+\frac{1}{2} \, \mathbf{a}_{3}$ | = | $- a x_{3} \,\mathbf{\hat{x}}- a x_{3} \,\mathbf{\hat{y}}+\frac{1}{2}c \,\mathbf{\hat{z}}$ | (4i) | I III |
| $\mathbf{B_{7}}$ | = | $x_{3} \, \mathbf{a}_{1}- x_{3} \, \mathbf{a}_{2}+\frac{1}{2} \, \mathbf{a}_{3}$ | = | $a x_{3} \,\mathbf{\hat{x}}- a x_{3} \,\mathbf{\hat{y}}+\frac{1}{2}c \,\mathbf{\hat{z}}$ | (4i) | I III |
| $\mathbf{B_{8}}$ | = | $- x_{3} \, \mathbf{a}_{1}+x_{3} \, \mathbf{a}_{2}+\frac{1}{2} \, \mathbf{a}_{3}$ | = | $- a x_{3} \,\mathbf{\hat{x}}+a x_{3} \,\mathbf{\hat{y}}+\frac{1}{2}c \,\mathbf{\hat{z}}$ | (4i) | I III |
| $\mathbf{B_{9}}$ | = | $x_{4} \, \mathbf{a}_{1}+z_{4} \, \mathbf{a}_{3}$ | = | $a x_{4} \,\mathbf{\hat{x}}+c z_{4} \,\mathbf{\hat{z}}$ | (4j) | Hg I |
| $\mathbf{B_{10}}$ | = | $- x_{4} \, \mathbf{a}_{1}+z_{4} \, \mathbf{a}_{3}$ | = | $- a x_{4} \,\mathbf{\hat{x}}+c z_{4} \,\mathbf{\hat{z}}$ | (4j) | Hg I |
| $\mathbf{B_{11}}$ | = | $- x_{4} \, \mathbf{a}_{2}- z_{4} \, \mathbf{a}_{3}$ | = | $- a x_{4} \,\mathbf{\hat{y}}- c z_{4} \,\mathbf{\hat{z}}$ | (4j) | Hg I |
| $\mathbf{B_{12}}$ | = | $x_{4} \, \mathbf{a}_{2}- z_{4} \, \mathbf{a}_{3}$ | = | $a x_{4} \,\mathbf{\hat{y}}- c z_{4} \,\mathbf{\hat{z}}$ | (4j) | Hg I |
References
- M. Hostettler, H. Birkedal, and D. Schwarzenbach, The structure of orange HgI$_{2}$. I. Polytypic layer structure, Acta Crystallogr. Sect. B 58, 903–913 (2002), doi:10.1107/S010876810201618X.
- D. Schwarzenbach, The crystal structure and one-dimensional disorder of the orange modification of HgI$_{2}$, Z. Kristallogr. 128, 97–114 (1969), doi:10.1524/zkri.1969.128.1-2.97.
- D. Schwarzenbach, H. Birkedal, M. Hostettler, and P. Fischer, Neutron diffraction investigation of the temperature dependence of crystal structure and thermal motions of red HgI$_{2}$, Acta Crystallogr. Sect. B 63, 826–835 (2007), doi:10.1107/S0108768107043327.
Found in
- P. Villars and K. Cenzual, Pearson's Crystal Data – Crystal Structure Database for Inorganic Compounds (2013). ASM International.
Prototype Generator
aflow --proto=AB2_tP12_115_j_egi --params=$a,c/a,z_{1},z_{2},x_{3},x_{4},z_{4}$