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MM: Fachverband Metall- und Materialphysik

MM 59: Computational Materials Modelling - Phase Stability III

MM 59.3: Vortrag

Donnerstag, 14. März 2013, 16:15–16:30, H24

Phase diagram and thermodynamic properties of aluminum nitride from ab initio calculations — •Steve Schmerler and Jens Kortus — TU Bergakademie Freiberg, Institut für Theoretische Physik, Leipziger Str. 23, 09599 Freiberg, Germany

The AlN system is of interest in the context of phase diagram studies of the Si–Al–O–N system where AlN is one important binary compound. Recent experiments have generated interest in the calculation of a P-T phase diagram for the AlN system in order to supplement the avaliable ab initio based data.

We used density functional perturbation theory in order to obtain the phonon density of states and the quasi-harmonic approximation to calculate thermodynamic properties of the low pressure wurtzite and high pressure rocksalt phase.

We present results on the P-T behavior of thermodynamic properties (heat capacity, bulk modulus, thermal expansion) and compare to experimental data. Especially, we show how the anisotropic thermal expansion of the wurtzite phase is calculated. A phase diagram constructed from calculated Gibbs enthalpy data for the wurtzite - rocksalt phase transition is presented. We also discuss the limits of the method and report results regarding the thermal stability of the high pressure phase.

We would like to thank the DFG for financial support within the DFG Priority Program 1236: Strukturen und Eigenschaften von Kristallen bei extrem hohen Drücken und Temperaturen