Figure 3.

Predicted phase stability for M′_4/3M′′_2/3AlB₂ alloys. (a) Calculated formation enthalpy at 0 K and (b) Gibbs free energy of formation at 2000 K. Symbols represent the crystal structure and chemical order of lowest energy for a given M′ and M′′: Cmmm with disorder (open squares), P6̅m2 with disorder (open hexagons), and in-plane-ordered i-MAB phases with P6̅2m (filled hexagons), P6̅2c (filled left triangles), R3̅m (filled up triangles), and C2 (filled down triangles) symmetries. Experimentally known phases are marked with squares: green (prior to this work) and yellow (this work).