# Encyclopedia of Crystallographic Prototypes

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)
D. Hicks, M. J. Mehl, E. Gossett, C. Toher, O. Levy, R. M. Hanson, G. L. W. Hart, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 2, Comp. Mat. Sci. 161, S1-S1011 (2019). (doi=10.1016/j.commatsci.2018.10.043)

## K2Pt(SCN)6 ($H6_{3}$) Structure : A2BC6_hP9_164_d_a_i

 Prototype : K2Pt(SCN)6 AFLOW prototype label : A2BC6_hP9_164_d_a_i Strukturbericht designation : $H6_{3}$ Pearson symbol : hP9 Space group number : 164 Space group symbol : $P\bar{3}m1$ AFLOW prototype command : aflow --proto=A2BC6_hP9_164_d_a_i --params=$a$,$c/a$,$z_{2}$,$x_{3}$,$z_{3}$

### Other compounds with this structure

• (NH4)2Pt(SCN)6 and Rb2Pt(SCN)6

• The structure here must be regarded at tentative. Even the official labeling of the structure is uncertain:
• (Hendricks, 1928) made the only structural study of this compound that we have been able to find. Unfortunately, they were not able to determine the positions of the carbon and silicon atoms. Presumably (SCN) forms a straight–line ionic system making a roughly 105° angle with the Pt–S line, as it does in the hydrated form of this compound K2Pt(SCN)6 · 2H2O.
• (Hendricks, 1928) were also uncertain about the space group, giving two possibilities: $P\overline{3}1m$ #162 and $P\overline{3}m1$ #164. They prefer the latter, so we present this as a $P\overline{3}m1$ #164 structure.
• The positions of the potassium and sulfur ions are not well determined. (Hendricks, 1928) give $z_{2} ≈ 0.5$, $x_{3} = 0.10–0.17$, and $z_{3} = 0.09–0.135$. We used the average values for the S–III coordinates.
• While (Ewald, 1931) gave this the Strukturbericht designation $H6_{3}$, (Hermann, 1937) lists it as $I1_{3}$, previously $H6_{3}$. However, they then go on to describe structures of the form SrCl2(H2O)6, with a very different $c/a$ ratio.
• (Ewald, 1931) originally used the $H6$ Strukturbericht category for compounds of the form B($X$)6, but (Herman, 1937) and following volumes use both $I$ and $J$ for B($X$)6, sometimes changing a previous $H6$ designation to $I1$ or $J1$. In general we will follow this change in notation, but given the striking difference in structures between K2Pt(SCN)6 and CaCl2(H2O)6 we will continue to use $H6_{3}$ for K2Pt(SCN)6 and $I1_{3}$ for CaCl2(H2O)6.

### Trigonal Hexagonal primitive vectors:

$\begin{array}{ccc} \mathbf{a}_1 & = & \frac12 \, a \, \mathbf{\hat{x}} - \frac{\sqrt3}2 \, a \, \mathbf{\hat{y}} \\ \mathbf{a}_2 & = & \frac12 \, a \, \mathbf{\hat{x}} + \frac{\sqrt3}2 \, a \, \mathbf{\hat{y}} \\ \mathbf{a}_3 & = & c \, \mathbf{\hat{z}} \\ \end{array}$

Basis vectors:

$\begin{array}{ccccccc} & & \mbox{Lattice Coordinates} & & \mbox{Cartesian Coordinates} &\mbox{Wyckoff Position} & \mbox{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) & \mbox{Pt} \\ \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{1}{2\sqrt{3}}a \, \mathbf{\hat{y}} + z_{2}c \, \mathbf{\hat{z}} & \left(2d\right) & \mbox{K} \\ \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{1}{2\sqrt{3}}a \, \mathbf{\hat{y}}-z_{2}c \, \mathbf{\hat{z}} & \left(2d\right) & \mbox{K} \\ \mathbf{B}_{4} & = & x_{3} \, \mathbf{a}_{1}-x_{3} \, \mathbf{a}_{2} + z_{3} \, \mathbf{a}_{3} & = & -\sqrt{3}x_{3}a \, \mathbf{\hat{y}} + z_{3}c \, \mathbf{\hat{z}} & \left(6i\right) & \mbox{S} \\ \mathbf{B}_{5} & = & x_{3} \, \mathbf{a}_{1} + 2x_{3} \, \mathbf{a}_{2} + z_{3} \, \mathbf{a}_{3} & = & \frac{3}{2}x_{3}a \, \mathbf{\hat{x}} + \frac{\sqrt{3}}{2}x_{3}a \, \mathbf{\hat{y}} + z_{3}c \, \mathbf{\hat{z}} & \left(6i\right) & \mbox{S} \\ \mathbf{B}_{6} & = & -2x_{3} \, \mathbf{a}_{1}-x_{3} \, \mathbf{a}_{2} + z_{3} \, \mathbf{a}_{3} & = & -\frac{3}{2}x_{3}a \, \mathbf{\hat{x}} + \frac{\sqrt{3}}{2}x_{3}a \, \mathbf{\hat{y}} + z_{3}c \, \mathbf{\hat{z}} & \left(6i\right) & \mbox{S} \\ \mathbf{B}_{7} & = & -x_{3} \, \mathbf{a}_{1} + x_{3} \, \mathbf{a}_{2}-z_{3} \, \mathbf{a}_{3} & = & \sqrt{3}x_{3}a \, \mathbf{\hat{y}}-z_{3}c \, \mathbf{\hat{z}} & \left(6i\right) & \mbox{S} \\ \mathbf{B}_{8} & = & 2x_{3} \, \mathbf{a}_{1} + x_{3} \, \mathbf{a}_{2}-z_{3} \, \mathbf{a}_{3} & = & \frac{3}{2}x_{3}a \, \mathbf{\hat{x}}-\frac{\sqrt{3}}{2}x_{3}a \, \mathbf{\hat{y}}-z_{3}c \, \mathbf{\hat{z}} & \left(6i\right) & \mbox{S} \\ \mathbf{B}_{9} & = & -x_{3} \, \mathbf{a}_{1}-2x_{3} \, \mathbf{a}_{2}-z_{3} \, \mathbf{a}_{3} & = & -\frac{3}{2}x_{3}a \, \mathbf{\hat{x}}-\frac{\sqrt{3}}{2}x_{3}a \, \mathbf{\hat{y}}-z_{3}c \, \mathbf{\hat{z}} & \left(6i\right) & \mbox{S} \\ \end{array}$

### References

• S. B. Hendricks and H. E. Merwin, The atomic arrangement in crystals of alkali platini–thiocyanates, Am. J. Sci. 15, 487–494 (1928), doi:10.2475/ajs.s5-15.90.487.
• P. P. Ewald and C. Hermann, eds., Strukturbericht 1913–1928 (Akademische Verlagsgesellschaft M. B. H., Leipzig, 1931).
• C. Hermann, O. Lohrmann, and H. Philipp, eds., Strukturbericht Band II 1928–1932 (Akademische Verlagsgesellschaft M. B. H., Leipzig, 1937).

### Found in

• P. P. Ewald and C. Hermann, eds., Strukturbericht 1913–1928 (Akademische Verlagsgesellschaft M. B. H., Leipzig, 1931).

### Prototype Generator

aflow --proto=A2BC6_hP9_164_d_a_i --params=