Computer Modelling of Energy Structure of Yb and Lu Doped LaF Crystals.

The energy band structure, as well as partial and total densities of states have been calculated for LaF:Yb and LaF:Lu crystals within density functional theory using the projector augmented wave method and Hubbard corrections (DFT + U). The influence of geometric optimization on the results of energy band calculations of LaF:Ln crystals (Ln = Yb, Lu) was analysed and the absence of relaxation procedure is confirmed to negatively influence the energy position of states, and the variability between obtained results of different optimization algorithms are within the calculation accuracy. The top of the valence band of LaF is confirmed to be formed by the 2pF-states and the bottom of the conduction band is formed by the 5d-states of La.

Energy Structure and Luminescence of CeF Crystals.

The results of the calculation of the energy band structure and luminescent research of CeF crystals are presented. The existence of two 5d1 and 5d2 subbands of the conduction band genetically derived from 5d states of Ce ions with different effective electron masses of 4.9 m and 0.