First principles phase diagram calculations for the wurtzite-structure systems AlN-GaN, GaN-InN, and AlN-InN

摘要

First principles phase diagram calculations were performed for the wurtzite-structure quasibinary systems AlN-GaN, GaN-InN, and AlN-InN. Cluster expansion Hamiltonians that excluded, and included, excess vibrational contributions to the free energy, F_(vib), were evaluated. Miscibility gaps are predicted for all three quasibinaries, with consolute points, (X_C,T_C), for AlN-GaN, GaN-InN, and AlN-InN equal to (0.50, 305 K), (0.50, 1850 K), and (0.50, 2830 K) without F_(vib), and (0.40, 247 K), (0.50, 1620 K), and (0.50, 2600 K) with F_(vib), respectively. In spite of the very different ionic radii of Al, Ga, and In, the GaN-InN and AlN-GaN diagrams are predicted to be approximately symmetric.