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 Combining double low line 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- Crossed D sign" indirect band gap. The main peaks in the imaginary part of the dielectric function correspond to the transition from the occupied state Fg'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.
Ghebouli, B., Fatmi, M., Ghebouli, M. A., Choutri, H., Louail, L., Chihi, T., … Bin-Omran, S. (2015). Theoretical study of the structural, elastic, electronic and optical properties of XCaF3 (X Combining double low line K and Rb). Solid State Sciences, 43, 9–14. https://doi.org/10.1016/j.solidstatesciences.2015.03.009