CuAu(I) ($L1_{0}$) Structure: AB_tP2_123_a_d-001
| Prototype | AuCu |
| AFLOW prototype label | AB_tP2_123_a_d-001 |
| Strukturbericht designation | $L1_{0}$ |
| ICSD | 42574 |
| Pearson symbol | tP2 |
| Space group number | 123 |
| Space group symbol | $P4/mmm$ |
| AFLOW prototype command |
aflow --proto=AB_tP2_123_a_d-001
--params=$a, \allowbreak c/a$ |
Other compounds with this structure
FePt, (Ni, Fe)Pt, (Cu, Fe)Pt, AgTi, AlTi, BiLi, BiNa, CoPt, EuIn, FePd, FePt, GaTi, HgPt, HgTi, HgZr, InPu, IrMn, IrNb, IrTi, IrV, MnNi, MnPt, MnRh, NiZn, NpSb, NiPt, PtV, PtZn, PuSb, RhTi, RuTa
- There can be considerable disorder in CuAu(I), as it can exist as Cu$_{1-x}$Au$_{x}$ with $0.44 < x < 0.56$. (Pearson, 1958; Bjerkelund, 1967)
- For $x > 0.5$ this transforms to the CuAu(II) phase above 390$^\circ$C. This phase is orthorhombic with $a$ and $c$ only changing slightly but $b ≈ 10 a$. This phase also exists at 200$^\circ$C for $0.33 < x < 0.65$, excluding the range where CuAu(I) forms. (Pearson, 1958)
- (Ewald, 1931) and later (Pearson, 1958) both doubled the unit cell and gave this structure the Pearson symbol $tP4$.
- $L1_{0}$ has $c/a ≈ \sqrt{2}$, characteristic of face-centered cubic ordering, while $L2_{a}$ has $c/a ≈ 1$, a body-centered cubic-like system. This structure has the same AFLOW designation, AB_tP2_123_a_d, as $\delta$–CuTi ($L2_{a}$). The only difference in the structures is the c/a ratio. They are generated by the same symmetry operations with different sets of parameters (
--params) specified in their corresponding CIF files. - We previously used the data from (Bayless, 1990), but we switched to (Bjerkelund, 1967) to match the ICSD entry.
\[ \begin{array}{ccc}
\mathbf{a_{1}}&=&a \,\mathbf{\hat{x}}\\\mathbf{a_{2}}&=&a \,\mathbf{\hat{y}}\\\mathbf{a_{3}}&=&c \,\mathbf{\hat{z}}
\end{array}\]
Basis vectors
| Lattice coordinates | Cartesian coordinates | Wyckoff position | Atom type | |||
|---|---|---|---|---|---|---|
| $\mathbf{B_{1}}$ | = | $0$ | = | $0$ | (1a) | Au I |
| $\mathbf{B_{2}}$ | = | $\frac{1}{2} \, \mathbf{a}_{1}+\frac{1}{2} \, \mathbf{a}_{2}+\frac{1}{2} \, \mathbf{a}_{3}$ | = | $\frac{1}{2}a \,\mathbf{\hat{x}}+\frac{1}{2}a \,\mathbf{\hat{y}}+\frac{1}{2}c \,\mathbf{\hat{z}}$ | (1d) | Cu I |
References
- E. Bjerkelund, W. B. Pearson, K. Selte, and A. Kjekshus, Lattice Parameters of the CuAu(I) Phase, Acta Chem. Scand. 21, 2900–2901 (1967), doi:10.3891/acta.chem.scand.21-2900.
- P. Bayliss, Revised Unit-Cell Dimensions, Space Group, and Chemical Formula of Some Metallic Materials, Can. Mineral. 28, 751–755 (1990).
- W. B. Pearson, A Handbook of Lattice Spacings and Structures of Metals and Alloys, International Series of Monographs on Metal Physics and Physical Metallurgy, vol. 4 (Pergamon Press, Oxford, London, Edinburgh, New York, Paris, Frankfort, 1958), 1964 reprint with corrections edn.
- P. P. Ewald and C. Hermann, eds., Strukturbericht 1913-1928 (Akademische Verlagsgesellschaft M. B. H., Leipzig, 1931).
Prototype Generator
aflow --proto=AB_tP2_123_a_d --params=$a,c/a$