First-principles elastic constants of α- and θ-Al2O3

Using an efficient strain-stress method, the first-principles elastic constants c(ij)'s of alpha-Al2O3 and theta-Al2O3 have been predicted within the local density approximation and the generalized gradient approximation. It is indicated that more accurate calculations of cij's can be accomplished by the local density approximation. The predicted c(ij)'s of alpha-Al2O3 provide helpful guidance for future measurements, especially the predicted negative c(15). The present results make the stress estimation in thermally grown oxides containing of alpha- and theta-Al2O3 possible, which in turn provide helpful insights for preventing the failure of thermal barrier coatings on components in gas-turbine engines. (c) 2007 American Institute of Physics.