Article,
Temperature-dependent elastic stiffness constants of α- and θ-Al 2 O 3 from first-principles calculations
Journal of Physics: Condensed Matter, 22 (37): 375403 (2010)
Abstract
Temperature-dependent elastic stiffness constants ( c ij s), including both the isothermal and isoentropic ones, have been predicted for rhombohedral α-Al 2 O 3 and monoclinic θ-Al 2 O 3 in terms of a quasistatic approach, i.e., a combination of volume-dependent c ij s determined by a first-principles strain versus stress method and direction-dependent thermal expansions obtained by first-principles phonon calculations. A good agreement is observed between the predictions and the available experiments for α-Al 2 O 3 , especially for the off-diagonal elastic constants. In addition, the temperature-dependent c ij s predicted herein, in particular the ones for metastable θ-Al 2 O 3 , enable the stress analysis at elevated temperatures in thermally grown oxides containing α- and θ-Al 2 O 3 , which are crucial to understand the failure of thermal barrier coatings in gas-turbine engines.
