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 |
| 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, $\alpha$-W$_{2}$C, Cd$_{2}$Ce, Cd$_{2}$La, Cd$_{2}$Pr, Cd$_{2}$Y, Cl$_{2}$Fe (HP), Ge$_{2}$Eu, $\gamma$-I$_{2}$Hg, S$_{2}$Hf, S$_{2}$Pt, S$_{2}$Sn (berndtite), S$_{2}$Ta, S$_{2}$Ti, S$_{2}$Zr, Se$_{2}$Hf, Se$_{2}$Pt, Se$_{2}$Sn, Se$_{2}$Ti, Se$_{2}$V, Se$_{2}$Zr, Te$_{2}$Co, Te$_{2}$Ir, Te$_{2}$Pd, Te$_{2}$Rh, Te$_{2}$Ti, Te$_{2}$V, Te$_{2}$Zn, Te$_{2}$Zr, NiSeTe, PdSeTe, SSeSn, (OH)$_{2}$Cd
- 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).
Prototype Generator
aflow --proto=AB2_hP3_164_a_d --params=$a,c/a,z_{2}$