$L1_{a}$ (disputed CuPt3) Structure : AB7_cF32_225_b_ad
| Prototype | : | CuPt3 |
| AFLOW prototype label | : | AB7_cF32_225_b_ad |
| Strukturbericht designation | : | $L1_{a}$ |
| Pearson symbol | : | cF32 |
| Space group number | : | 225 |
| Space group symbol | : | $Fm\bar{3}m$ |
| AFLOW prototype command | : | aflow --proto=AB7_cF32_225_b_ad --params=$a$ |
- According to (Tang, 1951), the ($24d$) sites have the composition Pt0.8Cu0.2 in stoichiometric CuPt3. Here we use
Pt
to specify the atoms on this site. - (Tang, 1951) states that the crystal structure of CuPt3 must be cubic, but (Mshumi, 2014) argue that it is orthorhombic, and in fact the $L1_{3}$ structure.
- (Smithells, 1955) gave this structure the $L1_{a}$ designation as part of his extension of the original Strukturbericht labels. He does note that an alternative orthorhombic structure had been proposed.
- (Smithells, 1955) assigns this structure to space group $F432$ #209, but the positions given by (Tang, 1951) are also consistent with $Fm\overline{3}m$ #225, so we assign this structure to the higher symmetry space group.
- (Tang, 1951) does not give the lattice constant, so we use the value estimated by (Smithells, 1955).
- The Wyckoff positions are identical to those of the Ca7Ge structure.
Face-centered Cubic primitive vectors:
\[ \begin{array}{ccc} \mathbf{a}_1 & = & \frac12 \, a \, \mathbf{\hat{y}} + \frac12 \, a \, \mathbf{\hat{z}} \\ \mathbf{a}_2 & = & \frac12 \, a \, \mathbf{\hat{x}} + \frac12 \, a \, \mathbf{\hat{z}} \\ \mathbf{a}_3 & = & \frac12 \, a \, \mathbf{\hat{x}} + \frac12 \, a \, \mathbf{\hat{y}} \\ \end{array} \]
Basis vectors:
\[ \begin{array}{ccccccc} & & \text{Lattice Coordinates} & & \text{Cartesian Coordinates} &\text{Wyckoff Position} & \text{Atom Type} \\ \mathbf{B}_{1} & = & 0 \, \mathbf{a}_{1} + 0 \, \mathbf{a}_{2} + 0 \, \mathbf{a}_{3} & = & 0 \, \mathbf{\hat{x}} + 0 \, \mathbf{\hat{y}} + 0 \, \mathbf{\hat{z}} & \left(4a\right) & \text{Pt I} \\ \mathbf{B}_{2} & = & \frac{1}{2} \, \mathbf{a}_{1} + \frac{1}{2} \, \mathbf{a}_{2} + \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{2}a \, \mathbf{\hat{x}} + \frac{1}{2}a \, \mathbf{\hat{y}} + \frac{1}{2}a \, \mathbf{\hat{z}} & \left(4b\right) & \text{Cu} \\ \mathbf{B}_{3} & = & \frac{1}{2} \, \mathbf{a}_{1} & = & \frac{1}{4}a \, \mathbf{\hat{y}} + \frac{1}{4}a \, \mathbf{\hat{z}} & \left(24d\right) & \text{Pt II} \\ \mathbf{B}_{4} & = & \frac{1}{2} \, \mathbf{a}_{2} + \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{2}a \, \mathbf{\hat{x}} + \frac{1}{4}a \, \mathbf{\hat{y}} + \frac{1}{4}a \, \mathbf{\hat{z}} & \left(24d\right) & \text{Pt II} \\ \mathbf{B}_{5} & = & \frac{1}{2} \, \mathbf{a}_{2} & = & \frac{1}{4}a \, \mathbf{\hat{x}} + \frac{1}{4}a \, \mathbf{\hat{z}} & \left(24d\right) & \text{Pt II} \\ \mathbf{B}_{6} & = & \frac{1}{2} \, \mathbf{a}_{1} + \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{4}a \, \mathbf{\hat{x}} + \frac{1}{2}a \, \mathbf{\hat{y}} + \frac{1}{4}a \, \mathbf{\hat{z}} & \left(24d\right) & \text{Pt II} \\ \mathbf{B}_{7} & = & \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{4}a \, \mathbf{\hat{x}} + \frac{1}{4}a \, \mathbf{\hat{y}} & \left(24d\right) & \text{Pt II} \\ \mathbf{B}_{8} & = & \frac{1}{2} \, \mathbf{a}_{1} + \frac{1}{2} \, \mathbf{a}_{2} & = & \frac{1}{4}a \, \mathbf{\hat{x}} + \frac{1}{4}a \, \mathbf{\hat{y}} + \frac{1}{2}a \, \mathbf{\hat{z}} & \left(24d\right) & \text{Pt II} \\ \end{array} \]References
- Y.–C. Tang, A cubic structure for the phase Pt3Cu, Acta Cryst. 4, 377–378 (1951), doi:10.1107/S0365110X51001185.
- C. J. Smithells, Metals Reference Book (Butterworths Scientific, London, 1955), second edn.
Found in
- C. Mshumi, C. I. Lang, L. R. Richey, K. C. Erb, C. W. Rosenbrock, L. J. Nelson, R. R. Vanfleet, H. T. Stokes, B. J. Campbell, and G. L. W. Hart, Revisiting the CuPt3 prototype and the $L1_{3}$ structure, Acta Mater. 73, 326–336 (2014), doi:10.1016/j.actamat.2014.03.029.