Ab initio study of mechanical and thermo-acoustic properties of tough ceramics: applications to HfO2 in its cubic and orthorhombic phase

By means of the ab initio all-electron new full-potential linear-muffin-tin orbitals method, calculations were made for elastic constants C11, C12 and C44 for Si, ZrO2 and HfO2 in their cubic phase, and constants C11, C22, C33, C12, C13, C23, C44, C55 and C66 for HfO2 in its orthorhombic phase. Using the Voigt and Reuss theory, estimations were made for polycrystals of their bulk, shear and Young moduli, and Poisson coefficients. The speed of elastic wave propagations and Debye temperatures were estimated for polycrystals built from Si and the above mentioned compounds. The semicore 4f14 electrons should be included in the valence set of Hf atom in this all-electron approach if accurate results for elastic properties under pressures are looked for