Abstract
The PLANE WAVE pseudo-potential method within density functional theory (DFT) has been used to investigate the structural, elastic, electronic and optical properties of XCaF3 (X = K and Rb) insulating. The studied compounds show a weak resistance to shear deformation compared to the resistance to the unidirectional compression. KCaF3 and RbCaF3 are considered ductile. The elastic constants and related parameters were predicted. The stiffness is more important in KCaF3, whereas, the lateral expansion is more important in RbCaF3. KCaF3 and RbCaF3 have R- Г indirect band gap. The main peaks in the imaginary part of the dielectric function correspond to the transition from the occupied state F−p to the unoccupied states Ca: s or K, Rb: p. At lower energies, KCaF3 and RbCaF3 show the same optical properties. Under pressure effect, the peaks of imaginary part of dielectric function were shifted toward high energy.
3D (in the ab-plane) directional dependence of the Young's modulus for RbCaF3. [Display omitted]
•A linear pressure dependence of the elastic stiffness's was observed.•KCaF3 and RbCaF3 are ductile materials and have an important lateral expansion.•We identified the main transitions from the occupied to the unoccupied states.•The effective masses of electrons and holes are respectively isotropic and anisotropic.