In this paper, we simulated the structural properties of the cubic impurity centers RE³⁺/RE²⁺ (RE = Rare earth) in fluorites crystals MeF₂ (Me = Ca, Sr, Ba) by ab initio route. Doping fluorite crystals with the rare-earth ion RE³⁺/RE²⁺, this replaces the cation Me²⁺ and determines distortions of the MeF₂ crystal lattice near the impurity center. These distortions characterized by radial and angular displacements of anions were investigated by ab initio method. We have employed the MO LCAO approach, in the frame of DFT method as it is implemented in the CRYSTAL17 software for periodic systems, using the hybrid functional PBE0. Since the main contribution to the crystal field on the rare-earth impurity ions comes from its nearest neighbors, the distance “rare-earth ion – ligand” and the radial and angular coordinates of the RE³⁺/RE²⁺ ions at several coordination spheres of anions near the impurity centers are calculated. Also, the changes in the local compressibility of the cationic and anionic sublattice next to the impurity ion are determined. The obtained results were discussed, compared with available experimental data and other theoretical results, and the agreement is quite satisfactory.

在本文中，我们通过从头算路线模拟了萤石晶体 MeF ₂ (Me = Ca, Sr, Ba) 中立方杂质中心 RE ³⁺ /RE ²⁺ (RE = 稀土)的结构特性。用稀土离子 RE ³⁺ /RE ²⁺掺杂萤石晶体，这取代了阳离子 Me ²⁺并确定了杂质中心附近MeF ₂晶格的畸变。这些以阴离子径向和角位移为特征的畸变是通过从头开始研究的方法。我们采用了 MO LCAO 方法，在 DFT 方法的框架内，因为它是在 CRYSTAL17 软件中实现的周期系统，使用混合功能 PBE0。由于稀土杂质离子对晶体场的主要贡献来自其最近的邻居，距离“稀土离子-配体”以及RE ³⁺ /RE ²⁺离子在几个配位处的径向和角坐标计算杂质中心附近的阴离子球。此外，还确定了杂质离子旁边的阳离子和阴离子亚晶格的局部可压缩性的变化。对得到的结果进行了讨论，与现有的实验数据和其他理论结果进行了比较，一致性比较令人满意。