Elastic properties of mono- and polycrystalline RCRh3 (R=Sc,Y,La and Lu) under pressure effect

The structural and elastic properties of perovskite-type RCRh3, with R=Sc, Y, La and Lu, under pressure effects have been investigated using the pseudo-potential plane-wave method based on the density functional theory within the generalized gradient approximation. For monocrystalline RCRh3, the optimized lattice constants, elastic constants and directional elastic wave velocities are calculated and analyzed in comparison with the available experimental and theoretical data. An increase in the lattice constant has been found with increasing atomic size of the R element and a corresponding decrease in the hardness. The anisotropic elastic constants and directional elastic wave velocities increase linearly with increasing pressure. A set of elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio, Lamé's coefficients, average sound velocity and Debye temperature are predicted in the framework of the Voigt-Reuss-Hill approximation for polycrystalline RCRh3. We have found that the toughness of RCRh3 compounds can be improved at high pressure.