Caswellsilverite (CrNaS2, $F5_{1}$) Crystal Structure: ABC2_hR4_166_a_b_c
| Prototype | : | CrNaS2 |
| AFLOW prototype label | : | ABC2_hR4_166_a_b_c |
| Strukturbericht designation | : | $F5_{1}$ |
| Pearson symbol | : | hR4 |
| Space group number | : | 166 |
| Space group symbol | : | $\text{R}\bar{3}\text{m}$ |
| AFLOW prototype command | : | aflow --proto=ABC2_hR4_166_a_b_c [--hex] --params=$a$,$c/a$,$x_{3}$ |
Other compounds with this structure
- AgAsSe2, AgAsSe2, AgBiSe2, AgBiTe2, AlCV2, BiTlSe2, BiTlTe2, CrNaSe2, CrRbS2, CrRbSe2, CsICl2, HoTlS2, InNaS2, InNaSe2, NaHF2, SbTlTe2, and TlYTe2
- This mineral did not obtain a name until it was discovered in nature (Okada, 1982). Caswellsilverite has the same AFLOW label, ABC2_hR4_166_a_b_c, as rhombohedral delafossite, CuFeO$_{2}$. The difference in the internal parameter $z_{3}$ causes a large change in the bonding of the two crystals, so we present them as different structures. Hexagonal settings of this structure can be obtained with the option ––hex.
Rhombohedral primitive vectors:
\[ \begin{array}{ccc} \mathbf{a}_1 & = & ~ \frac12 \, a \, \mathbf{\hat{x}} - \frac{1}{2\sqrt{3}} \, a \, \mathbf{\hat{y}} + \frac13 \, c \, \mathbf{\hat{z}} \\ \mathbf{a}_2 & = & \frac{1}{\sqrt{3}} \, a \, \mathbf{\hat{y}} + \frac13 \, c \, \mathbf{\hat{z}} \\ \mathbf{a}_3 & = & - \frac12 \, a \, \mathbf{\hat{x}} - \frac{1}{2\sqrt{3}} \, a \, \mathbf{\hat{y}} + \frac13 \, c \, \mathbf{\hat{z}} \\ \end{array} \]
Basis vectors:
\[ \begin{array}{ccccccc} & & \text{Lattice Coordinates} & & \text{Cartesian Coordinates} &\text{Wyckoff Position} & \text{Atom Type} \\ \mathbf{B}_{1} & =&0 \, \mathbf{a}_{1} + 0 \, \mathbf{a}_{2} + 0 \, \mathbf{a}_{3} & =&0 \mathbf{\hat{x}} + 0 \mathbf{\hat{y}} + 0 \mathbf{\hat{z}} & \left(1a\right) & \text{Cr} \\ \mathbf{B}_{2} & =&\frac12 \, \mathbf{a}_{1}+ \frac12 \, \mathbf{a}_{2}+ \frac12 \, \mathbf{a}_{3}& =&\frac12 \, c \, \mathbf{\hat{z}}& \left(1b\right) & \text{Na} \\ \mathbf{B}_{3} & =&x_{3} \, \mathbf{a}_{1}+ x_{3} \, \mathbf{a}_{2}+ x_{3} \, \mathbf{a}_{3}& =&x_{3} \, c \, \mathbf{\hat{z}}& \left(2c\right) & \text{S} \\ \mathbf{B}_{4} & =&- x_{3} \, \mathbf{a}_{1}- x_{3} \, \mathbf{a}_{2}- x_{3} \, \mathbf{a}_{3}& =&- x_{3} \, c \, \mathbf{\hat{z}}& \left(2c\right) & \text{S} \\ \end{array} \]References
- A. Okada and K. Keil, Caswellsilverite, NaCrS2: a new mineral in the Norton County enstatite achondrite, Am. Mineral. 67, 132–136 (1982).
- F. M. R. Engelsman, G. A. Wiegers, F. Jellinek, and B. Van 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.
Found in
- R. T. Downs and M. Hall–Wallace, The American Mineralogist Crystal Structure Database, Am. Mineral. 88, 247–250 (2003).