Caswellsilverite (CrNaS$_{2}$, $F5_{1}$) Structure: ABC2_hR4_166_a_b_c-001
| Prototype | CrNaS$_{2}$ |
| AFLOW prototype label | ABC2_hR4_166_a_b_c-001 |
| Strukturbericht designation | $F5_{1}$ |
| Mineral name | caswellsilverite |
| ICSD | 42389 |
| Pearson symbol | hR4 |
| Space group number | 166 |
| Space group symbol | $R\overline{3}m$ |
| AFLOW prototype command |
aflow --proto=ABC2_hR4_166_a_b_c-001
--params=$a, \allowbreak c/a, \allowbreak x_{3}$ |
Other compounds with this structure
AgBiSe$_{2}$, AgBiTe$_{2}$, AlCV$_{2}$, BiTlSe$_{2}$, BiTlTe$_{2}$, CrNaSe$_{2}$, CrRbS$_{2}$, CrRbSe$_{2}$, CsICl$_{2}$, FeNiO$_{2}$, HNaF$_{2}$, HoTlS$_{2}$, InNaS$_{2}$, InNaSe$_{2}$, NaHF$_{2}$, SbTlTe$_{2}$, TlYTe$_{2}$, TlS (HP), TlSe (HP)
- The name caswellsilverite was not used until natural samples of the mineral were found. (Okada, 1982).
- Caswellsilverite has the same AFLOW label, ABC2_hR4_166_a_b_c, as rhombohedral delafossite, CuFeO$_{2}$ and $\alpha$–NaFeO$_{2}$. The difference in the internal parameter $z_{3}$ between CuFeO$_{2}$ and CrNaS$_{2}$ causes a large change in the bonding of the two crystals, so we present them as different structures.
- The structures are generated by the same symmetry operations with different sets of parameters (
--params) specified in their corresponding CIF files. - Hexagonal settings of this structure can be obtained with the option
--hex.
\[ \begin{array}{ccc}
\mathbf{a_{1}}&=&\frac{1}{2}a \,\mathbf{\hat{x}}- \frac{\sqrt{3}}{6}a \,\mathbf{\hat{y}}+\frac{1}{3}c \,\mathbf{\hat{z}}\\\mathbf{a_{2}}&=&\frac{1}{\sqrt{3}}a \,\mathbf{\hat{y}}+\frac{1}{3}c \,\mathbf{\hat{z}}\\\mathbf{a_{3}}&=&- \frac{1}{2}a \,\mathbf{\hat{x}}- \frac{\sqrt{3}}{6}a \,\mathbf{\hat{y}}+\frac{1}{3}c \,\mathbf{\hat{z}}
\end{array}\]
Basis vectors
| Lattice coordinates | Cartesian coordinates | Wyckoff position | Atom type | |||
|---|---|---|---|---|---|---|
| $\mathbf{B_{1}}$ | = | $0$ | = | $0$ | (1a) | Cr I |
| $\mathbf{B_{2}}$ | = | $\frac{1}{2} \, \mathbf{a}_{1}+\frac{1}{2} \, \mathbf{a}_{2}+\frac{1}{2} \, \mathbf{a}_{3}$ | = | $\frac{1}{2}c \,\mathbf{\hat{z}}$ | (1b) | Na I |
| $\mathbf{B_{3}}$ | = | $x_{3} \, \mathbf{a}_{1}+x_{3} \, \mathbf{a}_{2}+x_{3} \, \mathbf{a}_{3}$ | = | $c x_{3} \,\mathbf{\hat{z}}$ | (2c) | S I |
| $\mathbf{B_{4}}$ | = | $- x_{3} \, \mathbf{a}_{1}- x_{3} \, \mathbf{a}_{2}- x_{3} \, \mathbf{a}_{3}$ | = | $- c x_{3} \,\mathbf{\hat{z}}$ | (2c) | S I |
References
- F. Engelsman, G. Wiegers, F. Jellinek, and B. V. Laar, Crystal structures and magnetic structures of some metal(I) chromium(III) sulfides and selenides, J. Solid State Chem. 6, 574–582 (1973), doi:10.1016/S0022-4596(73)80018-0.
- A. Okada and K. Keil, Caswellsilverite, NaCrS$_2$: a new mineral in the Norton County enstatite achondrite, Am. Mineral. 67, 132–136 (1982).
Found in
- R. T. Downs and M. Hall-Wallace, The American Mineralogist Crystal Structure Database, Am. Mineral. 88, 247–250 (2003).
Prototype Generator
aflow --proto=ABC2_hR4_166_a_b_c --params=$a,c/a,x_{3}$