ω Phase (CdI$_{2}$, $C6$) Structure: AB2_hP3_164_a_d-001
| Prototype | CdI$_{2}$ |
| AFLOW prototype label | AB2_hP3_164_a_d-001 |
| Strukturbericht designation | $C6$ |
| ICSD | 53983 |
| CCDC | 1618603 |
| Pearson symbol | hP3 |
| Space group number | 164 |
| Space group symbol | $P\overline{3}m1$ |
| AFLOW prototype command |
aflow --proto=AB2_hP3_164_a_d-001
--params=$a, \allowbreak c/a, \allowbreak z_{2}$ |
Other compounds with this structure
Ti, Zr, Hf, ZrNb, TiNb, TiV, CaI$_{2}$, Cd$_{2}$Ce, Cd$_{2}$La, Cd(OH)$_{2}$, Cd$_{2}$Pr, Cd$_{2}$Y, CdI$_{2}$, CoBr$_{2}$, CoI$_{2}$, CoO$_{2}$, CoTe$_{2}$, CrSe$_{2}$, EuGe$_{2}$, FeBr$_{2}$, FeCl$_{2}$ (HP), FeI$_{2}$, HfS$_{2}$, HfSe$_{2}$, HfTe$_{2}$, γ-HgI$_{2}$, IrTe$_{2}$, MgBr$_{2}$, MgCl$_{2}$, MgI$_{2}$, MnBr$_{2}$, MnI$_{2}$, Nb$_{2}$C, NbS$_{2}$, NbSe$_{2}$, NbTe$_{2}$, NiTe$_{2}$, PbI$_{2}$, PdTe$_{2}$, PtS$_{2}$, PtSe$_{2}$, RhTe$_{2}$, SiS$_{2}$, SiTe$_{2}$, SnS$_{2}$ (berndtite), SnS$_{2}$, SnSe$_{2}$, Ta$_{2}$C, TaS$_{2}$, TaSe$_{2}$, Ti$_{2}$O, TiBr$_{2}$, TiCl$_{2}$, TiS$_{2}$, TiSe$_{2}$, TiTe$_{2}$, TmI$_{2}$, V$_{2}$C, VBr$_{2}$, VCl$_{2}$, VI$_{2}$, VS$_{2}$, VSe$_{2}$, VTe$_{2}$, α-W$_{2}$C, YbI$_{2}$, ZnI$_{2}$, ZnTe$_{2}$, ZrS$_{2}$, ZrSe$_{2}$, ZrTe$_{2}$, BiTeBr, NiSeTe, PdSeTe, SSeSn, TiSeTe
- The $\omega$ phase can be either hexagonal ($C32$) or trigonal (shown here). The trigonal $\omega$ phase transforms into several high-symmetry structures under certain conditions:
${\mathbf c/a}$ ${\mathbf z}$ Lattice Arbitrary $\frac12$ Ideal Omega ($C32$) $\sqrt{\frac38}$ $\frac16$ Body-Centered Cubic ($A2$) $\sqrt{\frac32}$ $\frac16$ Simple Cubic ($A_{h}$) $\sqrt{6}$ $\frac16$ Face-Centered Cubic ($A1$) Arbitrary 0 Simple Hexagonal Structure ($A_{f}$)
- For more details about the omega phase and materials which form in the omega phase, see (Sikka, 1982) . As noted there, most omega phase intermetallic alloys are disordered. Although the
$\omega$
label comes from $\omega$–CrTi, (Ewald, 1931) lists the prototype for Strukturbericht designation $C6$ as CdI$_{2}$. - Alternative stackings for CdI$_{2}$ have been proposed, including a $6H$ stacking and the questionable $C27$ structure.
\[ \begin{array}{ccc}
\mathbf{a_{1}}&=&\frac{1}{2}a \,\mathbf{\hat{x}}- \frac{\sqrt{3}}{2}a \,\mathbf{\hat{y}}\\\mathbf{a_{2}}&=&\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{\sqrt{3}}{2}a \,\mathbf{\hat{y}}\\\mathbf{a_{3}}&=&c \,\mathbf{\hat{z}}
\end{array}\]
Basis vectors
| Lattice coordinates | Cartesian coordinates | Wyckoff position | Atom type | |||
|---|---|---|---|---|---|---|
| $\mathbf{B_{1}}$ | = | $0$ | = | $0$ | (1a) | Cd I |
| $\mathbf{B_{2}}$ | = | $\frac{1}{3} \, \mathbf{a}_{1}+\frac{2}{3} \, \mathbf{a}_{2}+z_{2} \, \mathbf{a}_{3}$ | = | $\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{\sqrt{3}}{6}a \,\mathbf{\hat{y}}+c z_{2} \,\mathbf{\hat{z}}$ | (2d) | I I |
| $\mathbf{B_{3}}$ | = | $\frac{2}{3} \, \mathbf{a}_{1}+\frac{1}{3} \, \mathbf{a}_{2}- z_{2} \, \mathbf{a}_{3}$ | = | $\frac{1}{2}a \,\mathbf{\hat{x}}- \frac{\sqrt{3}}{6}a \,\mathbf{\hat{y}}- c z_{2} \,\mathbf{\hat{z}}$ | (2d) | I I |
References
- R. M. Bozorth, The Crystal Structure of Cadmium Iodide, J. Am. Chem. Soc. 44, 2232–2236 (1922), doi:10.1021/ja01431a019.
- S. K. Sikka, Y. K. Vohra, and R. Chidambaram, Omega Phase in Materials, Prog. Mater. Sci. 27, 245–310 (1982), doi:10.1016/0079-6425(82)90002-0.
Found in
- P. P. Ewald and C. Hermann, eds., Strukturbericht 1913-1928 (Akademische Verlagsgesellschaft M. B. H., Leipzig, 1931).
First cited in
- M. J. Mehl, D. Hicks, C. Toher, O. Levy, R. M. Hanson, G. L. W. Hart, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 1, Comp. Mat. Sci. 136, S1-S828 (2017). (doi=10.1016/j.commatsci.2017.01.017)
Geometry files
Prototype Generator
aflow --proto=AB2_hP3_164_a_d --params=$a,c/a,z_{2}$