Pressure effect on electronic, elastic and optical properties of Eu: CaF2 crystal: a first-principles study

The structure, electronic structure, elastic and optical properties of pure CaF2 and Eu:CaF2 are investigated by performing the generalized gradient approximation in the frame of density functional theory. The obtained lattice constant, band structure, elastic constants and imaginary part of dielectric function of pure CaF2 agree well with the experimental and other theoretical results. These properties of Eu:CaF2 are also calculated, and it follows that Eu doping leads to the crystal structure distorted, as well as the spin polarization of the system. Especially an impurity band is introduced in the bandgap, above the Fermi level, in the band structure of the Eu:CaF2, narrowing the bandgap. In addition, it is observed that the optical peaks of Eu:CaF2 shift towards the longer wavelength side, and the peak intensities drop compared with pure CaF2. Furthermore, Eu doping induces a series of new peaks in the optical properties, which is probably caused by the transitions of the 4f electrons of the Eu atoms. It is worth mentioning that the effect of pressure on the optical properties of Eu:CaF2 is also studied, we can hold that the optical peaks will have a blueshift.