Room Temperature KBD$_{4}$ Structure: AB8C_cF40_225_a_f_b-001
| Prototype | BH$_{4}$K |
| AFLOW prototype label | AB8C_cF40_225_a_f_b-001 |
| ICSD | 99263 |
| Pearson symbol | cF40 |
| Space group number | 225 |
| Space group symbol | $Fm\overline{3}m$ |
| AFLOW prototype command |
aflow --proto=AB8C_cF40_225_a_f_b-001
--params=$a, \allowbreak x_{3}$ |
Other compounds with this structure
CsBD$_{4}$, CsBH$_{4}$, KBH$_{4}$, LaBH$_{8}$, NaBD$_{4}$, NaBH$_{4}$, RbBD$_{4}$, RbBH$_{4}$
- This is the room-temperature phase of all of these structures.
- Below 70K KBD$_{4}$ transforms into a tetragonal structure with the deuterium atoms forming a tetrahedron around the boron, but this is not seen for (Cs,Na,Rb)BD$_{4}$ or (Cs,Na,Rb)BH$_{4}$, where the system remains cubic (Renaudin, 2004).
- In all of the ABD$_{4}$ structures the deuterium atoms only occupy half of the (32f) sites. (Soldate, 1954) suggests that in the H$_{4}$ compounds the hydrogen atoms form a rotating tetrahedra around the boron atoms.
- (Di Cataldo, 2021) predict LaBH$_{8}$ forms in this structure at pressures around 50 GPa, where it would superconduct with $T_{c} = 126$K. In this case the (32f) sites are fully filled.
- Most authors use NaBH$_{4}$ as the prototype, but since (Renaudin, 2004) provide information on the location of the deuterium atoms we use KBD$_{4}$, with data taken at room temperature, we use this as the prototype.
\[ \begin{array}{ccc}
\mathbf{a_{1}}&=&\frac{1}{2}a \,\mathbf{\hat{y}}+\frac{1}{2}a \,\mathbf{\hat{z}}\\\mathbf{a_{2}}&=&\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{z}}\\\mathbf{a_{3}}&=&\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}
\end{array}\]
Basis vectors
| Lattice coordinates | Cartesian coordinates | Wyckoff position | Atom type | |||
|---|---|---|---|---|---|---|
| $\mathbf{B_{1}}$ | = | $0$ | = | $0$ | (4a) | B I |
| $\mathbf{B_{2}}$ | = | $\frac{1}{2} \, \mathbf{a}_{1}+\frac{1}{2} \, \mathbf{a}_{2}+\frac{1}{2} \, \mathbf{a}_{3}$ | = | $\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}+\frac{1}{2}a \,\mathbf{\hat{z}}$ | (4b) | K I |
| $\mathbf{B_{3}}$ | = | $x_{3} \, \mathbf{a}_{1}+x_{3} \, \mathbf{a}_{2}+x_{3} \, \mathbf{a}_{3}$ | = | $a x_{3} \,\mathbf{\hat{x}}+a x_{3} \,\mathbf{\hat{y}}+a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
| $\mathbf{B_{4}}$ | = | $x_{3} \, \mathbf{a}_{1}+x_{3} \, \mathbf{a}_{2}- 3 x_{3} \, \mathbf{a}_{3}$ | = | $- a x_{3} \,\mathbf{\hat{x}}- a x_{3} \,\mathbf{\hat{y}}+a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
| $\mathbf{B_{5}}$ | = | $x_{3} \, \mathbf{a}_{1}- 3 x_{3} \, \mathbf{a}_{2}+x_{3} \, \mathbf{a}_{3}$ | = | $- a x_{3} \,\mathbf{\hat{x}}+a x_{3} \,\mathbf{\hat{y}}- a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
| $\mathbf{B_{6}}$ | = | $- 3 x_{3} \, \mathbf{a}_{1}+x_{3} \, \mathbf{a}_{2}+x_{3} \, \mathbf{a}_{3}$ | = | $a x_{3} \,\mathbf{\hat{x}}- a x_{3} \,\mathbf{\hat{y}}- a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
| $\mathbf{B_{7}}$ | = | $- x_{3} \, \mathbf{a}_{1}- x_{3} \, \mathbf{a}_{2}+3 x_{3} \, \mathbf{a}_{3}$ | = | $a x_{3} \,\mathbf{\hat{x}}+a x_{3} \,\mathbf{\hat{y}}- a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
| $\mathbf{B_{8}}$ | = | $- x_{3} \, \mathbf{a}_{1}- x_{3} \, \mathbf{a}_{2}- x_{3} \, \mathbf{a}_{3}$ | = | $- a x_{3} \,\mathbf{\hat{x}}- a x_{3} \,\mathbf{\hat{y}}- a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
| $\mathbf{B_{9}}$ | = | $- x_{3} \, \mathbf{a}_{1}+3 x_{3} \, \mathbf{a}_{2}- x_{3} \, \mathbf{a}_{3}$ | = | $a x_{3} \,\mathbf{\hat{x}}- a x_{3} \,\mathbf{\hat{y}}+a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
| $\mathbf{B_{10}}$ | = | $3 x_{3} \, \mathbf{a}_{1}- x_{3} \, \mathbf{a}_{2}- x_{3} \, \mathbf{a}_{3}$ | = | $- a x_{3} \,\mathbf{\hat{x}}+a x_{3} \,\mathbf{\hat{y}}+a x_{3} \,\mathbf{\hat{z}}$ | (32f) | D I |
References
- G. Renaudin, S. Gomes, H. Hagemann, L. Keller, and K. Yvon, Structural and spectroscopic studies on the alkali borohydrides MBH$_{4}$ (M = Na, K, Rb, Cs), J. Alloys Compd. 375, 98–106 (2004), doi:10.1016/j.jallcom.2003.11.018.
- A. M. Soldate, Crystal Structure of Sodium Borohydride, J. Am. Chem. Soc. 69, 987–988 (1954), doi:10.1021/ja01197a002.
Found in
- S. D. Cataldo, C. Heil, W. von der Linden, and L. Boeri, LaBH$_{8}$: the first high-T$_{c}$ low-pressure superhydride, Phys. Rev. B 104, L020511 (2021), doi:10.1103/PhysRevB.104.L020511.
Prototype Generator
aflow --proto=AB8C_cF40_225_a_f_b --params=$a,x_{3}$