Structural and elastic properties of orthorhombic CaGeO3 under pressure from first principles

The structural and elastic properties of the orthorhombic CaGeO3 under pressure are investigated by the plane wave pseudopotential density functional theory (DFT) within the local density approximation (LDA) and the generalized gradient approximation (GGA). The calculated lattice parameters and unit-cell volume V0 of the orthorhombic CaGeO3 at 0 GPa and 0 K are in good agreement with the available experimental data and other theoretical data. The pressure dependences of elastic constants, bulk modulus, shear modulus, compressional and shear wave velocities are systematically investigated for the first time. It is found that the orthorhombic CaGeO3 maintains brittle properties under the applied pressures. The analysis for the calculated elastic constants has been made to reveal the mechanical stability and mechanical anisotropy of the orthorhombic CaGeO3 up to 100 GPa