First Principle Calculation of $4{\rm f}^{\rm n}\rightarrow 4{\rm f}^{({\rm n}-1)}5{\rm d}$ Absorption Spectra of ${\rm Ce}^{3+}$ and ${\rm Pr}^{3+}$ Ions in Alkaline Earth Fluorides

In this paper we present the results of an ab initio calculations of df-absorption spectra for alkaline earth fluoride matrix doped with
${\rm Pr}^{3+}$
and
${\rm Ce}^{3+}$
ions. The density-functional theory (DFT) calculations have been performed in embedded-cluster approach. All our results were obtained with taking into account the lattice relaxation in the presence of trivalent impurity ion. The calculation have been made both for cubic and tetragonal centers. For the tetragonal centers we estimate the crystal field splitting of
$e_{g}$
level.