Structural and elastic properties of LaAlO3 from first-principles calculations

Using the first-principles linearized augmented plane wave calculations within density functional theory, the stable structure, the phase transition, and elastic properties of the LaAlO3 are investigated. At low temperature, our calculation indicates that the rhombohedral R-3C phase is the most energetically stable structure among the three proposed structures: R-3C (No. 167), R-3M (No. 166), and R3C (No. 161). It is found that the LaAlO3 transforms from rhombohedral R-3C phase to cubic PM-3M phase with a volume change of 1% when the applied hydrostatic pressure is 15.4 GPa, which is consistent with the experimental value. The elastic constants, shear modulus, bulk modulus, and Poisson's ratio of LaAlO3 are calculated and compared with corresponding experimental data. Our result shows that the rotation of the AlO6 octahedra in LaAlO3 has a large influence on the anisotropic elastic constants. From the calculated Debye temperature and elastic constants, the R-3C phase of LaAlO3 is predicted to be more thermostable and to exhibit higher fracture toughness than the high-pressured PM-3M phase. (c) 2008 American Institute of Physics.